Method And User Equipment For Receiving Donwlink Signal, Method And Base Station For Transmitting Downlink Signal

ABSTRACT

A user equipment is provided with puncturing information indicating a resource to which downlink data is punctured among time-frequency resources to which the downlink data is allocated. The user equipment may decode the downlink data received in the time-frequency resource on the basis of the puncturing information. The downlink data may be mapped to the time-frequency resource by a combined method of a time-first resource mapping method and a frequency-first resource mapping method, or by a distributed resource mapping method.

TECHNICAL FIELD

The present invention relates to a wireless communication system, andmore particularly, to a method and apparatus for transmitting/receivinga downlink signal.

BACKGROUND ART

With appearance and spread of machine-to-machine (M2M) communication anda variety of devices such as smartphones and tablet PCs and technologydemanding a large amount of data transmission, data throughput needed ina cellular network has rapidly increased. To satisfy such rapidlyincreasing data throughput, carrier aggregation technology, cognitiveradio technology, etc. for efficiently employing more frequency bandsand multiple input multiple output (MIMO) technology, multi-base station(BS) cooperation technology, etc. for raising data capacity transmittedon limited frequency resources have been developed.

A general wireless communication system performs datatransmission/reception through one downlink (DL) band and through oneuplink (UL) band corresponding to the DL band (in case of a frequencydivision duplex (FDD) mode), or divides a prescribed radio frame into aUL time unit and a DL time unit in the time domain and then performsdata transmission/reception through the UL/DL time unit (in case of atime division duplex (TDD) mode). A base station (BS) and a userequipment (UE) transmit and receive data and/or control informationscheduled on a prescribed time unit basis, e.g. on a subframe basis. Thedata is transmitted and received through a data region configured in aUL/DL subframe and the control information is transmitted and receivedthrough a control region configured in the UL/DL subframe. To this end,various physical channels carrying radio signals are formed in the UL/DLsubframe. In contrast, carrier aggregation technology serves to use awider UL/DL bandwidth by aggregating a plurality of UL/DL frequencyblocks in order to use a broader frequency band so that more signalsrelative to signals when a single carrier is used can be simultaneouslyprocessed.

In addition, a communication environment has evolved into increasingdensity of nodes accessible by a user at the periphery of the nodes. Anode refers to a fixed point capable of transmitting/receiving a radiosignal to/from the UE through one or more antennas. A communicationsystem including high-density nodes may provide a better communicationservice to the UE through cooperation between the nodes.

As more communication devices have demanded higher communicationcapacity, there has been necessity of enhanced mobile broadband (eMBB)relative to legacy radio access technology (RAT). In addition, massivemachine type communication (mMTC) for providing various services atanytime and anywhere by connecting a plurality of devices and objects toeach other is one main issue to be considered in next generationcommunication.

Further, a communication system to be designed in consideration of aservice/UE sensitive to reliability and standby time is underdiscussion. Introduction of next generation radio access technology hasbeen discussed by taking into consideration eMBB communication, mMTC,ultra-reliable and low-latency communication (URLLC), and the like.

DISCLOSURE Technical Problem

Due to introduction of new radio communication technology, the number ofuser equipments (UEs) to which a BS should provide a service in aprescribed resource region increases and the amount of data and controlinformation that the BS should transmit to the UEs increases. Since theamount of resources available to the BS for communication with the UE(s)is limited, a new method in which the BS efficiently receives/transmitsuplink/downlink data and/or uplink/downlink control information usingthe limited radio resources is needed.

With development of technologies, overcoming delay or latency has becomean important challenge. Applications whose performance criticallydepends on delay/latency are increasing. Accordingly, a method to reducedelay/latency compared to the legacy system is demanded.

Also, with development of smart devices, a new scheme for efficientlytransmitting/receiving a small amount of data or efficientlytransmitting/receiving data occurring at a low frequency is required.

In addition, a signal transmission/reception method is required in thesystem supporting new radio access technologies (NR).

The technical objects that can be achieved through the present inventionare not limited to what has been particularly described hereinabove andother technical objects not described herein will be more clearlyunderstood by persons skilled in the art from the following detaileddescription.

Technical Solution

According to an aspect of the present invention, provided herein is amethod of receiving a downlink signal by a user equipment. The methodincludes receiving puncturing information indicating a resource on whichdownlink data is punctured among time-frequency resources to which thedownlink data is allocated; and decoding the downlink data receivedwithin the time-frequency resources based on the puncturing information.

According to another aspect of the present invention, provided herein isa user equipment for receiving a downlink signal. The user equipmentincludes a radio frequency (RF) unit, and a processor configured tocontrol the RF unit. The processor: controls the RF unit to receivepuncturing information indicating a resource on which downlink data ispunctured among time-frequency resources to which the downlink data isallocated; and decodes the downlink data received within thetime-frequency resources based on the puncturing information.

According to another aspect of the present invention, provided herein isa method of transmitting a downlink signal by a base station. The methodincludes: transmitting downlink data to a user equipment by puncturing apart of time-frequency resources to which the downlink data isallocated; and transmitting puncturing information indicating a resourceon which the downlink data is punctured to the user equipment.

According to another aspect of the present invention, provided herein isa base station for transmitting a downlink signal. The base stationincludes a radio frequency (RF) unit, and a processor configured tocontrol the RF unit. The processor: controls the RF unit to transmitdownlink data to a user equipment by puncturing a part of time-frequencyresources to which the downlink data is allocated; and controls the RFunit to transmit puncturing information indicating a resource on whichthe downlink data is punctured to the user equipment.

According to another aspect of the present invention, provided herein isa method of receiving a downlink signal by a user equipment. The methodincludes receiving downlink data on a time-frequency resource allocatedto the user equipment; and recovering the downlink data mapped to thetime-frequency resource. The downlink data is mapped to thetime-frequency resource by a combination resource mapping scheme or adistributed resource mapping scheme. The combination resource mappingscheme maps the downlink data by a time-first frequency-second mappingscheme in each of X time regions included in a time-frequency resourceregion, X being an integer greater than 1. The distributed resourcemapping scheme maps the downlink data in a diagonal direction in thetime-frequency resource region.

According to another aspect of the present invention, provided herein isa user equipment for receiving a downlink signal. The user equipmentincludes a radio frequency (RF) unit, and a processor configured tocontrol the RF unit. The processor: controls the RF unit to receivedownlink data on a time-frequency resource allocated to the userequipment; and recovers the downlink data mapped to the time-frequencyresource. The downlink data is mapped to the time-frequency resource bya combination resource mapping scheme or a distributed resource mappingscheme. The combination resource mapping scheme maps the downlink databy a time-first frequency-second mapping scheme in each of X timeregions included in a time-frequency resource region, X being an integergreater than 1. The distributed resource mapping scheme maps thedownlink data in a diagonal direction in the time-frequency resourceregion.

According to another aspect of the present invention, provided herein isa method of transmitting a downlink signal by a base station. The methodincludes mapping downlink data to a time-frequency resource allocated toa user equipment; and transmitting the downlink data mapped to thetime-frequency resource. The downlink data is mapped to thetime-frequency resource by a combination resource mapping scheme or adistributed resource mapping scheme. The combination resource mappingscheme maps the downlink data by a time-first frequency-second mappingscheme in each of X time regions included in a time-frequency resourceregion, X being an integer greater than 1. The distributed resourcemapping scheme maps the downlink data in a diagonal direction in thetime-frequency resource region.

According to another aspect of the present invention, provided herein isa base station for transmitting a downlink signal. The base stationincludes a radio frequency (RF) unit, and a processor configured tocontrol the RF unit. The processor: maps downlink data to atime-frequency resource allocated to a user equipment; and controls theRF unit to transmit the downlink data mapped to the time-frequencyresource. The downlink data is mapped to the time-frequency resource bya combination resource mapping scheme or a distributed resource mappingscheme. The combination resource mapping scheme maps the downlink databy a time-first frequency-second mapping scheme in each of X timeregions included in a time-frequency resource region, X being an integergreater than 1. The distributed resource mapping scheme maps thedownlink data in a diagonal direction in the time-frequency resourceregion.

In each aspect of the present invention, the time-frequency resourcesmay span one or more orthogonal frequency division multiplexing (OFDM)symbol groups each including one or more OFDM symbols in a time domain.The puncturing information may indicate a punctured OFDM symbol groupamong the one or more OFDM symbol groups.

In each aspect of the present invention, the puncturing information maybe transmitted or received on a puncturing channel received on apunctured OFDM symbol group basis.

In each aspect of the present invention, the base station may nottransmit the puncturing channel with respect to an OFDM symbol group onwhich the downlink data is punctured and may transmit the puncturingchannel with respect to an OFDM symbol group on which the downlink datais not punctured. Upon detecting the puncturing channel for an OFDMsymbol group, the user equipment may determine that the downlink data ispresent on the OFDM symbol group. Upon not detecting the puncturingchannel for an OFDM symbol group, the user equipment may decode thedownlink data under the assumption that the downlink data is punctured.

In each aspect of the present invention, the puncturing information mayindicate a resource punctured by data using numerology different fromnumerology of the downlink data.

In each aspect of the present invention, the puncturing information maybe received or transmitted in a next downlink transmission time interval(TTI) of a downlink TTI in which the downlink data is received ortransmitted.

In each aspect of the present invention, scheduling information aboutuplink data which is to be transmitted in a TTI shorter than a TTI of abasic length may be transmitted to the user equipment. The userequipment may transmit the uplink data at maximum transmission power orspecific transmission power.

In each aspect of the present invention, information indicating X may betransmitted to the user equipment.

In each aspect of the present invention, the downlink data may besegmented into one or more code blocks and X may be determined based onthe number of code blocks.

In each aspect of the present invention, the distributed resourcemapping scheme sequentially may map the downlink data to a resourceelement (m_(i+1), n_(i+1))=((m_(i)+a) mod M, (n_(i)+b) mod N) startingfrom a resource element (m₁, n₁) in the time-frequency resource region,m₁ being a lowest subcarrier index in the time-frequency resource regionand n₁ being a lowest orthogonal frequency division multiplexing (OFDM)symbol index in the time-frequency resource region. The resource element(m_(i+1), n_(i+1)) may be an (i+1)-th resource element to which thedownlink data is mapped in the time-frequency resource region, M beingthe number of subcarriers in the time-frequency resource region, N beingthe number of OFDM symbols in the time-frequency resource region, and aand b being positive integers.

In each aspect of the present invention, a may be 1 and b may be 1.

In each aspect of the present invention, the downlink data may besegmented into a plurality of code blocks and the plural code blocks maybe interleaved and then mapped in the time-frequency resource region.

The above technical solutions are merely some parts of the embodimentsof the present invention and various embodiments into which thetechnical features of the present invention are incorporated can bederived and understood by persons skilled in the art from the followingdetailed description of the present invention.

Advantageous Effects

According to the present invention, uplink/downlink signals can beefficiently transmitted/received. Therefore, overall throughput of aradio communication system can be improved.

According to an embodiment of the present invention, delay/latencyoccurring during communication between a user equipment and a basestation may be reduced.

In addition, owing to development of smart devices, it is possible toefficiently transmit/receive not only a small amount of data but alsodata which occurs infrequently.

Moreover, signals can be transmitted/received in the NR system.

It will be appreciated by persons skilled in the art that that theeffects that can be achieved through the present invention are notlimited to what has been particularly described hereinabove and otheradvantages of the present invention will be more clearly understood fromthe following detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention, illustrate embodiments of the inventionand together with the description serve to explain the principle of theinvention.

FIG. 1 illustrates the structure of a radio frame used in the LTE/LTE-Abased wireless communication system.

FIG. 2 illustrates the structure of a downlink (DL)/uplink (UL) slot inthe LTE/LTE-A based wireless communication system.

FIG. 3 illustrates the structure of a DL subframe used in the LTE/LTE-Abased wireless communication system.

FIG. 4 illustrates the structure of a UL subframe used in the LTE/LTE-Abased wireless communication system.

FIG. 5 illustrates an example of a short TTI and a transmission exampleof a control channel and a data channel in the short TTI.

FIG. 6 illustrates the structure of an available subframe in a new radioaccess technology (NR) system.

FIG. 7 illustrates an application example of analog beamforming.

FIG. 8 illustrates collision caused by transmission of data of twodifferent types on the same time-frequency resource.

FIG. 9 illustrates an example of indicating a punctured OFDM symbolregion according to the present invention.

FIG. 10 illustrates a resource mapping method according to the presentinvention.

FIG. 11 is a block diagram illustrating elements of a transmittingdevice 10 and a receiving device 20 for implementing the presentinvention.

MODE FOR CARRYING OUT THE INVENTION

Reference will now be made in detail to the exemplary embodiments of thepresent invention, examples of which are illustrated in the accompanyingdrawings. The detailed description, which will be given below withreference to the accompanying drawings, is intended to explain exemplaryembodiments of the present invention, rather than to show the onlyembodiments that can be implemented according to the invention. Thefollowing detailed description includes specific details in order toprovide a thorough understanding of the present invention. However, itwill be apparent to those skilled in the art that the present inventionmay be practiced without such specific details.

In some instances, known structures and devices are omitted or are shownin block diagram form, focusing on important features of the structuresand devices, so as not to obscure the concept of the present invention.The same reference numbers will be used throughout this specification torefer to the same or like parts.

The following techniques, apparatuses, and systems may be applied to avariety of wireless multiple access systems. Examples of the multipleaccess systems include a code division multiple access (CDMA) system, afrequency division multiple access (FDMA) system, a time divisionmultiple access (TDMA) system, an orthogonal frequency division multipleaccess (OFDMA) system, a single carrier frequency division multipleaccess (SC-FDMA) system, and a multicarrier frequency division multipleaccess (MC-FDMA) system. CDMA may be embodied through radio technologysuch as universal terrestrial radio access (UTRA) or CDMA2000. TDMA maybe embodied through radio technology such as global system for mobilecommunications (GSM), general packet radio service (GPRS), or enhanceddata rates for GSM evolution (EDGE). OFDMA may be embodied through radiotechnology such as institute of electrical and electronics engineers(IEEE) 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20, or evolved UTRA(E-UTRA). UTRA is a part of a universal mobile telecommunications system(UMTS). 3rd generation partnership project (3GPP) long term evolution(LTE) is a part of evolved UMTS (E-UMTS) using E-UTRA. 3GPP LTE employsOFDMA in DL and SC-FDMA in UL. LTE-advanced (LTE-A) is an evolvedversion of 3GPP LTE. For convenience of description, it is assumed thatthe present invention is applied to 3GPP LTE/LTE-A. However, thetechnical features of the present invention are not limited thereto. Forexample, although the following detailed description is given based on amobile communication system corresponding to a 3GPP LTE/LTE-A system,aspects of the present invention that are not specific to 3GPP LTE/LTE-Aare applicable to other mobile communication systems.

For example, the present invention is applicable to contention basedcommunication such as Wi-Fi as well as non-contention basedcommunication as in the 3GPP LTE/LTE-A system in which an eNB allocatesa DL/UL time/frequency resource to a UE and the UE receives a DL signaland transmits a UL signal according to resource allocation of the eNB.In a non-contention based communication scheme, an access point (AP) ora control node for controlling the AP allocates a resource forcommunication between the UE and the AP, whereas, in a contention basedcommunication scheme, a communication resource is occupied throughcontention between UEs which desire to access the AP. The contentionbased communication scheme will now be described in brief. One type ofthe contention based communication scheme is carrier sense multipleaccess (CSMA). CSMA refers to a probabilistic media access control (MAC)protocol for confirming, before a node or a communication devicetransmits traffic on a shared transmission medium (also called a sharedchannel) such as a frequency band, that there is no other traffic on thesame shared transmission medium. In CSMA, a transmitting devicedetermines whether another transmission is being performed beforeattempting to transmit traffic to a receiving device. In other words,the transmitting device attempts to detect presence of a carrier fromanother transmitting device before attempting to perform transmission.Upon sensing the carrier, the transmitting device waits for anothertransmission device which is performing transmission to finishtransmission, before performing transmission thereof. Consequently, CSMAcan be a communication scheme based on the principle of “sense beforetransmit” or “listen before talk”. A scheme for avoiding collisionbetween transmitting devices in the contention based communicationsystem using CSMA includes carrier sense multiple access with collisiondetection (CSMA/CD) and/or carrier sense multiple access with collisionavoidance (CSMA/CA). CSMA/CD is a collision detection scheme in a wiredlocal area network (LAN) environment. In CSMA/CD, a personal computer(PC) or a server which desires to perform communication in an Ethernetenvironment first confirms whether communication occurs on a networkand, if another device carries data on the network, the PC or the serverwaits and then transmits data. That is, when two or more users (e.g.PCs, UEs, etc.) simultaneously transmit data, collision occurs betweensimultaneous transmission and CSMA/CD is a scheme for flexiblytransmitting data by monitoring collision. A transmitting device usingCSMA/CD adjusts data transmission thereof by sensing data transmissionperformed by another device using a specific rule. CSMA/CA is a MACprotocol specified in IEEE 802.11 standards. A wireless LAN (WLAN)system conforming to IEEE 802.11 standards does not use CSMA/CD whichhas been used in IEEE 802.3 standards and uses CA, i.e. a collisionavoidance scheme. Transmission devices always sense carrier of a networkand, if the network is empty, the transmission devices wait fordetermined time according to locations thereof registered in a list andthen transmit data. Various methods are used to determine priority ofthe transmission devices in the list and to reconfigure priority. In asystem according to some versions of IEEE 802.11 standards, collisionmay occur and, in this case, a collision sensing procedure is performed.A transmission device using CSMA/CA avoids collision between datatransmission thereof and data transmission of another transmissiondevice using a specific rule.

In embodiments of the present invention described below, the term“assume” may mean that a subject to transmit a channel transmits thechannel in accordance with the corresponding “assumption”. This may alsomean that a subject to receive the channel receives or decodes thechannel in a form conforming to the “assumption”, on the assumption thatthe channel has been transmitted according to the “assumption”.

In the present invention, puncturing a channel on a specific resourcemeans that the signal of the channel is mapped to the specific resourcein the procedure of resource mapping of the channel, but a portion ofthe signal mapped to the punctured resource is excluded in transmittingthe channel. In other words, the specific resource which is punctured iscounted as a resource for the channel in the procedure of resourcemapping of the channel, a signal mapped to the specific resource amongthe signals of the channel is not actually transmitted. The receiver ofthe channel receives, demodulates or decodes the channel, assuming thatthe signal mapped to the specific resource is not transmitted. On theother hand, rate-matching of a channel on a specific resource means thatthe channel is never mapped to the specific resource in the procedure ofresource mapping of the channel, and thus the specific resource is notused for transmission of the channel. In other words, the rate-matchedresource is not counted as a resource for the channel in the procedureof resource mapping of the channel. The receiver of the channelreceives, demodulates, or decodes the channel, assuming that thespecific rate-matched resource is not used for mapping and transmissionof the channel.

In the present invention, a user equipment (UE) may be a fixed or mobiledevice. Examples of the UE include various devices that transmit andreceive user data and/or various kinds of control information to andfrom a base station (BS). The UE may be referred to as a terminalequipment (TE), a mobile station (MS), a mobile terminal (MT), a userterminal (UT), a subscriber station (SS), a wireless device, a personaldigital assistant (PDA), a wireless modem, a handheld device, etc. Inaddition, in the present invention, a BS generally refers to a fixedstation that performs communication with a UE and/or another BS, andexchanges various kinds of data and control information with the UE andanother BS. The BS may be referred to as an advanced base station (ABS),a node-B (NB), an evolved node-B (eNB), a base transceiver system (BTS),an access point (AP), a processing server (PS), etc. Particularly, eNBis a term used to denote a BS supporting LTE radio access technology andgNB is a term used to denote a BS supporting new radio access technologynetwork (NR). In describing the present invention, a BS will be referredto as an eNB.

In the present invention, a node refers to a fixed point capable oftransmitting/receiving a radio signal through communication with a UE.Various types of eNBs may be used as nodes irrespective of the termsthereof. For example, a BS, a node B (NB), an e-node B (eNB), apico-cell eNB (PeNB), a home eNB (HeNB), a relay, a repeater, etc. maybe a node. In addition, the node may not be an eNB. For example, thenode may be a radio remote head (RRH) or a radio remote unit (RRU). TheRRH or RRU generally has a lower power level than a power level of aneNB. Since the RRH or RRU (hereinafter, RRH/RRU) is generally connectedto the eNB through a dedicated line such as an optical cable,cooperative communication between RRH/RRU and the eNB can be smoothlyperformed in comparison with cooperative communication between eNBsconnected by a radio line. At least one antenna is installed per node.The antenna may mean a physical antenna or mean an antenna port or avirtual antenna.

In the present invention, a cell refers to a prescribed geographicalarea to which one or more nodes provide a communication service.Accordingly, in the present invention, communicating with a specificcell may mean communicating with an eNB or a node which provides acommunication service to the specific cell. In addition, a DL/UL signalof a specific cell refers to a DL/UL signal from/to an eNB or a nodewhich provides a communication service to the specific cell. A nodeproviding UL/DL communication services to a UE is called a serving nodeand a cell to which UL/DL communication services are provided by theserving node is especially called a serving cell. Furthermore, channelstatus/quality of a specific cell refers to channel status/quality of achannel or communication link formed between an eNB or node whichprovides a communication service to the specific cell and a UE. The UEmay measure DL channel state received from a specific node usingcell-specific reference signal(s) (CRS(s)) transmitted on a CRS resourceand/or channel state information reference signal(s) (CSI-RS(s))transmitted on a CSI-RS resource, allocated by antenna port(s) of thespecific node to the specific node. Detailed CSI-RS configuration may beunderstood with reference to 3GPP TS 36.211 and 3GPP TS 36.331documents.

Meanwhile, a 3GPP LTE/LTE-A system uses the concept of a cell in orderto manage radio resources and a cell associated with the radio resourcesis distinguished from a cell of a geographic region.

A “cell” of a geographic region may be understood as coverage withinwhich a node can provide service using a carrier and a “cell” of a radioresource is associated with bandwidth (BW) which is a frequency rangeconfigured by the carrier. Since DL coverage, which is a range withinwhich the node is capable of transmitting a valid signal, and ULcoverage, which is a range within which the node is capable of receivingthe valid signal from the UE, depends upon a carrier carrying thesignal, the coverage of the node may be associated with coverage of the“cell” of a radio resource used by the node. Accordingly, the term“cell” may be used to indicate service coverage of the node sometimes, aradio resource at other times, or a range that a signal using a radioresource can reach with valid strength at other times.

Meanwhile, the 3GPP LTE-A standard uses the concept of a cell to manageradio resources. The “cell” associated with the radio resources isdefined by combination of downlink resources and uplink resources, thatis, combination of DL CC and UL CC. The cell may be configured bydownlink resources only, or may be configured by downlink resources anduplink resources. If carrier aggregation is supported, linkage between acarrier frequency of the downlink resources (or DL CC) and a carrierfrequency of the uplink resources (or UL CC) may be indicated by systeminformation. For example, combination of the DL resources and the ULresources may be indicated by linkage of system information block type 2(SIB2). The carrier frequency means a center frequency of each cell orCC. A cell operating on a primary frequency may be referred to as aprimary cell (Pcell) or PCC, and a cell operating on a secondaryfrequency may be referred to as a secondary cell (Scell) or SCC. Thecarrier corresponding to the Pcell on downlink will be referred to as adownlink primary CC (DL PCC), and the carrier corresponding to the Pcellon uplink will be referred to as an uplink primary CC (UL PCC). A Scellmeans a cell that may be configured after completion of radio resourcecontrol (RRC) connection establishment and used to provide additionalradio resources. The Scell may form a set of serving cells for the UEtogether with the Pcell in accordance with capabilities of the UE. Thecarrier corresponding to the Scell on the downlink will be referred toas downlink secondary CC (DL SCC), and the carrier corresponding to theScell on the uplink will be referred to as uplink secondary CC (UL SCC).Although the UE is in RRC-CONNECTED state, if it is not configured bycarrier aggregation or does not support carrier aggregation, a singleserving cell configured by the Pcell only exists.

3GPP LTE/LTE-A standards define DL physical channels corresponding toresource elements carrying information derived from a higher layer andDL physical signals corresponding to resource elements which are used bya physical layer but which do not carry information derived from ahigher layer. For example, a physical downlink shared channel (PDSCH), aphysical broadcast channel (PBCH), a physical multicast channel (PMCH),a physical control format indicator channel (PCFICH), a physicaldownlink control channel (PDCCH), and a physical hybrid ARQ indicatorchannel (PHICH) are defined as the DL physical channels, and a referencesignal and a synchronization signal are defined as the DL physicalsignals. A reference signal (RS), also called a pilot, refers to aspecial waveform of a predefined signal known to both a BS and a UE. Forexample, a cell-specific RS (CRS), a UE-specific RS (UE-RS), apositioning RS (PRS), and channel state information RS (CSI-RS) may bedefined as DL RSs. Meanwhile, the 3GPP LTE/LTE-A standards define ULphysical channels corresponding to resource elements carryinginformation derived from a higher layer and UL physical signalscorresponding to resource elements which are used by a physical layerbut which do not carry information derived from a higher layer. Forexample, a physical uplink shared channel (PUSCH), a physical uplinkcontrol channel (PUCCH), and a physical random access channel (PRACH)are defined as the UL physical channels, and a demodulation referencesignal (DM RS) for a UL control/data signal and a sounding referencesignal (SRS) used for UL channel measurement are defined as the ULphysical signals.

In the present invention, a physical downlink control channel (PDCCH), aphysical control format indicator channel (PCFICH), a physical hybridautomatic retransmit request indicator channel (PHICH), and a physicaldownlink shared channel (PDSCH) refer to a set of time-frequencyresources or resource elements (REs) carrying downlink controlinformation (DCI), a set of time-frequency resources or REs carrying acontrol format indicator (CFI), a set of time-frequency resources or REscarrying downlink acknowledgement (ACK)/negative ACK (NACK), and a setof time-frequency resources or REs carrying downlink data, respectively.In addition, a physical uplink control channel (PUCCH), a physicaluplink shared channel (PUSCH) and a physical random access channel(PRACH) refer to a set of time-frequency resources or REs carryinguplink control information (UCI), a set of time-frequency resources orREs carrying uplink data and a set of time-frequency resources or REscarrying random access signals, respectively. In the present invention,in particular, a time-frequency resource or RE that is assigned to orbelongs to PDCCH/PCFICH/PHICH/PDSCH/PUCCH/PUSCH/PRACH is referred to asPDCCH/PCFICH/PHICH/PDSCH/PUCCH/PUSCH/PRACH RE orPDCCH/PCFICH/PHICH/PDSCH/PUCCH/PUSCH/PRACH time-frequency resource,respectively. Therefore, in the present invention, PUCCH/PUSCH/PRACHtransmission of a UE is conceptually identical to UCI/uplink data/randomaccess signal transmission on PUSCH/PUCCH/PRACH, respectively. Inaddition, PDCCH/PCFICH/PHICH/PDSCH transmission of an eNB isconceptually identical to downlink data/DCI transmission onPDCCH/PCFICH/PHICH/PDSCH, respectively.

Hereinafter, OFDM symbol/subcarrier/RE to or for whichCRS/DMRS/CSI-RS/SRS/UE-RS/TRS is assigned or configured will be referredto as CRS/DMRS/CSI-RS/SRS/UE-RS/TRS symbol/carrier/subcarrier/RE. Forexample, an OFDM symbol to or for which a tracking RS (TRS) is assignedor configured is referred to as a TRS symbol, a subcarrier to or forwhich the TRS is assigned or configured is referred to as a TRSsubcarrier, and an RE to or for which the TRS is assigned or configuredis referred to as a TRS RE. In addition, a subframe configured fortransmission of the TRS is referred to as a TRS subframe. Moreover, asubframe in which a broadcast signal is transmitted is referred to as abroadcast subframe or a PBCH subframe and a subframe in which asynchronization signal (e.g. PSS and/or SSS) is transmitted is referredto a synchronization signal subframe or a PSS/SSS subframe. OFDMsymbol/subcarrier/RE to or for which PSS/SSS is assigned or configuredis referred to as PSS/SSS symbol/subcarrier/RE, respectively.

In the present invention, a CRS port, a UE-RS port, a CSI-RS port, and aTRS port refer to an antenna port configured to transmit a CRS, anantenna port configured to transmit a UE-RS, an antenna port configuredto transmit a CSI-RS, and an antenna port configured to transmit a TRS,respectively. Antenna ports configured to transmit CRSs may bedistinguished from each other by the locations of REs occupied by theCRSs according to CRS ports, antenna ports configured to transmit UE-RSsmay be distinguished from each other by the locations of REs occupied bythe UE-RSs according to UE-RS ports, and antenna ports configured totransmit CSI-RSs may be distinguished from each other by the locationsof REs occupied by the CSI-RSs according to CSI-RS ports. Therefore, theterm CRS/UE-RS/CSI-RS/TRS ports may also be used to indicate a patternof REs occupied by CRSs/UE-RSs/CSI-RSs/TRSs in a predetermined resourceregion. In the present invention, both a DMRS and a UE-RS refer to RSsfor demodulation and, therefore, the terms DMRS and UE-RS are used torefer to RSs for demodulation.

For terms and technologies which are not specifically described amongthe terms of and technologies employed in this specification, 3GPPLTE/LTE-A standard documents, for example, 3GPP TS 36.211, 3GPP TS36.212, 3GPP TS 36.213, 3GPP TS 36.321 and 3GPP TS 36.331 may bereferenced.

FIG. 1 illustrates the structure of a radio frame used in a wirelesscommunication system.

Specifically, FIG. 1(a) illustrates an exemplary structure of a radioframe which can be used in frequency division multiplexing (FDD) in 3GPPLTE/LTE-A and FIG. 1(b) illustrates an exemplary structure of a radioframe which can be used in time division multiplexing (TDD) in 3GPPLTE/LTE-A.

Referring to FIG. 1, a 3GPP LTE/LTE-A radio frame is 10 ms (307,200T_(s)) in duration. The radio frame is divided into 10 subframes ofequal size. Subframe numbers may be assigned to the 10 subframes withinone radio frame, respectively. Here, T_(s) denotes sampling time whereT_(s)=1/(2048*15 kHz). Each subframe is 1 ms long and is further dividedinto two slots. 20 slots are sequentially numbered from 0 to 19 in oneradio frame. Duration of each slot is 0.5 ms. A time interval in whichone subframe is transmitted is defined as a transmission time interval(TTI). Time resources may be distinguished by a radio frame number (orradio frame index), a subframe number (or subframe index), a slot number(or slot index), and the like.

A TTI refers to an interval at which data may be scheduled. For example,the transmission opportunity of a UL grant or DL grant is given every 1ms in the current LTE/LTE-A system. The UL/DL grant opportunity is notgiven several times within a time shorter than 1 ms. Accordingly, theTTI is 1 ms in the current LTE-LTE-A system.

A radio frame may have different configurations according to duplexmodes. In FDD mode for example, since DL transmission and ULtransmission are discriminated according to frequency, a radio frame fora specific frequency band operating on a carrier frequency includeseither DL subframes or UL subframes. In TDD mode, since DL transmissionand UL transmission are discriminated according to time, a radio framefor a specific frequency band operating on a carrier frequency includesboth DL subframes and UL subframes.

FIG. 2 illustrates the structure of a DL/UL slot structure in theLTE/LTE-A based wireless communication system.

Referring to FIG. 2, a slot includes a plurality of orthogonal frequencydivision multiplexing (OFDM) symbols in the time domain and includes aplurality of resource blocks (RBs) in the frequency domain. The OFDMsymbol may refer to one symbol duration. Referring to FIG. 2, a signaltransmitted in each slot may be expressed by a resource grid includingN^(DL/UL) _(RB)N^(RB) _(sc) subcarriers and N^(DL/UL) _(symb) OFDMsymbols. N^(DL) _(RB) denotes the number of RBs in a DL slot and N^(UL)_(RB) denotes the number of RBs in a UL slot. N^(DL) _(RB) and N^(UL)_(RB) depend on a DL transmission bandwidth and a UL transmissionbandwidth, respectively. N^(DL) _(symb) denotes the number of OFDMsymbols in a DL slot, N^(UL) _(symb) denotes the number of OFDM symbolsin a UL slot, and N^(RB) _(sc) denotes the number of subcarriersconfiguring one RB.

An OFDM symbol may be referred to as an OFDM symbol, a single carrierfrequency division multiplexing (SC-FDM) symbol, etc. according tomultiple access schemes. The number of OFDM symbols included in one slotmay be varied according to channel bandwidths and CP lengths. Forexample, in a normal cyclic prefix (CP) case, one slot includes 7 OFDMsymbols. In an extended CP case, one slot includes 6 OFDM symbols.Although one slot of a subframe including 7 OFDM symbols is shown inFIG. 2 for convenience of description, embodiments of the presentinvention are similarly applicable to subframes having a differentnumber of OFDM symbols. Referring to FIG. 2, each OFDM symbol includesN^(DL/UL) _(RB)*N^(RB) _(sc) subcarriers in the frequency domain. Thetype of the subcarrier may be divided into a data subcarrier for datatransmission, a reference signal (RS) subcarrier for RS transmission,and a null subcarrier for a guard band and a DC component. The nullsubcarrier for the DC component is unused and is mapped to a carrierfrequency f₀ in a process of generating an OFDM signal or in a frequencyup-conversion process. The carrier frequency is also called a centerfrequency f_(c).

FIG. 3 illustrates the structure of a DL subframe used in a wirelesscommunication system.

Referring to FIG. 3, a DL subframe is divided into a control region anda data region in the time domain. Referring to FIG. 3, a maximum of 3(or 4) OFDM symbols located in a front part of a first slot of asubframe corresponds to the control region. Hereinafter, a resourceregion for PDCCH transmission in a DL subframe is referred to as a PDCCHregion. OFDM symbols other than the OFDM symbol(s) used in the controlregion correspond to the data region to which a physical downlink sharedchannel (PDSCH) is allocated. Hereinafter, a resource region availablefor PDSCH transmission in the DL subframe is referred to as a PDSCHregion.

Examples of a DL control channel used in 3GPP LTE include a physicalcontrol format indicator channel (PCFICH), a physical downlink controlchannel (PDCCH), a physical hybrid ARQ indicator channel (PHICH), etc.

The control information transmitted through the PDCCH will be referredto as downlink control information (DCI). The DCI includes resourceallocation information for a UE or UE group and other controlinformation. Transmit format and resource allocation information of adownlink shared channel (DL-SCH) are referred to as DL schedulinginformation or DL grant. Transmit format and resource allocationinformation of an uplink shared channel (UL-SCH) are referred to as ULscheduling information or UL grant. The size and usage of the DCIcarried by one PDCCH are varied depending on DCI formats. The size ofthe DCI may be varied depending on a coding rate. In the current 3GPPLTE system, various formats are defined, wherein formats 0 and 4 aredefined for a UL, and formats 1, 1A, 1B, 1C, 1D, 2, 2A, 2B, 2C, 3 and 3Aare defined for a DL. Combination selected from control information suchas a hopping flag, RB allocation, modulation coding scheme (MCS),redundancy version (RV), new data indicator (NDI), transmit powercontrol (TPC), cyclic shift, cyclic shift demodulation reference signal(DM RS), UL index, channel quality information (CQI) request, DLassignment index, HARQ process number, transmitted precoding matrixindicator (TPMI), precoding matrix indicator (PMI) information istransmitted to the UE as the DCI. The following table shows examples ofDCI formats.

A plurality of PDCCHs may be transmitted within a control region. A UEmay monitor the plurality of PDCCHs. An eNB determines a DCI formatdepending on the DCI to be transmitted to the UE, and attaches cyclicredundancy check (CRC) to the DCI. The CRC is masked (or scrambled) withan identifier (for example, a radio network temporary identifier (RNTI))depending on usage of the PDCCH or owner of the PDCCH. For example, ifthe PDCCH is for a specific UE, the CRC may be masked with an identifier(for example, cell-RNTI (C-RNTI)) of the corresponding UE. If the PDCCHis for a paging message, the CRC may be masked with a paging identifier(for example, paging-RNTI (P-RNTI)). If the PDCCH is for systeminformation (in more detail, system information block (SIB)), the CRCmay be masked with system information RNTI (SI-RNTI). If the PDCCH isfor a random access response, the CRC may be masked with a random accessRNTI (RA-RNTI). For example, CRC masking (or scrambling) includes XORoperation of CRC and RNTI at the bit level.

Generally, a DCI format, which may be transmitted to the UE, is varieddepending on a transmission mode configured for the UE. In other words,certain DCI format(s) corresponding to the specific transmission modenot all DCI formats may only be used for the UE configured to a specifictransmission mode.

The PDCCH is allocated to the first m OFDM symbol(s) in a subframe.Herein, m is an integer equal to or greater than 1 and is indicated by aPCFICH.

The PCFICH carries information about the number of OFDM symbols that DCIcarried by the PDCCH spans. The PCFICH is transmitted on the first OFDMsymbol of a subframe and carries information about the number of OFDMsymbols used to transmit a control channel in a subframe. The PCFICHindicates, to the UE, the number of OFDM symbols used in a correspondingsubframe with respect to every subframe. The PCFICH is located on thefirst OFDM symbol. The PCFICH is configured by 4 resource element groups(REGs) and each REG is distributed in a control region based on a cellID. One REG includes 4 REs.

The PDCCH is transmitted on an aggregation of one or a plurality ofcontinuous control channel elements (CCEs). The CCE is a logicallocation unit used to provide a coding rate based on the status of aradio channel to the PDCCH. The CCE corresponds to a plurality ofresource element groups (REGs). For example, each CCE contains 9 REGs,which are distributed across the first 1/2/3 (/4 if needed for a 1.4 MHzchannel) OFDM symbols and the system bandwidth through interleaving toenable diversity and to mitigate interference. One REG corresponds tofour REs. Four QPSK symbols are mapped to each REG. A resource element(RE) occupied by the reference signal (RS) is not included in the REG.Accordingly, the number of REGs within given OFDM symbols is varieddepending on the presence of the RS. The REGs are also used for otherdownlink control channels (that is, PDFICH and PHICH).

Assuming that the number of REGs not allocated to the PCFICH or thePHICH is N_(REG), the number of available CCEs in a DL subframe forPDCCH(s) in a system is numbered from 0 to N_(CCE)-1, whereN_(CCE)=floor(N_(REG)/9). A PDCCH including n consecutive CCEs may betransmitted only on CCEs fulfilling “i mod n=0” wherein i is a CCEnumber.

A PDCCH format and the number of DCI bits are determined in accordancewith the number of CCEs. The CCEs are numbered and consecutively used.To simplify the decoding process, a PDCCH having a format including nCCEs may be initiated only on CCEs assigned numbers corresponding tomultiples of n. The number of CCEs used for transmission of a specificPDCCH is determined by a network or the eNB in accordance with channelstatus. For example, one CCE may be required for a PDCCH for a UE (forexample, adjacent to eNB) having a good downlink channel. However, incase of a PDCCH for a UE (for example, located near the cell edge)having a poor channel, eight CCEs may be required to obtain sufficientrobustness. Additionally, a power level of the PDCCH may be adjusted tocorrespond to a channel status.

In a 3GPP LTE/LTE-A system, a set of CCEs on which a PDCCH can belocated for each UE is defined. A CCE set in which the UE can detect aPDCCH thereof is referred to as a PDCCH search space or simply as asearch space (SS). An individual resource on which the PDCCH can betransmitted in the SS is called a PDCCH candidate. A set of PDCCHcandidates that the UE is to monitor is defined in terms of SSs, where asearch space S^((L)) _(k) at aggregation level L∈{1,2,4,8} is defined bya set of PDCCH candidates. SSs for respective PDCCH formats may havedifferent sizes and a dedicated SS and a common SS are defined. Thededicated SS is a UE-specific SS (USS) and is configured for eachindividual UE. The common SS (CSS) is configured for a plurality of UEs.

DCI formats that the UE should monitor depend on a transmission modeconfigured per serving cell. The eNB transmits an actual PDCCH (DCI) ona PDCCH candidate in a search space and the UE monitors the search spaceto detect the PDCCH (DCI). Here, monitoring implies attempting to decodeeach PDCCH in the corresponding SS according to DCI format(s) which theUE shall monitor. The UE may detect a PDCCH thereof by monitoring aplurality of PDCCHs. Basically, the UE does not know the location atwhich a PDCCH thereof is transmitted. Therefore, the UE attempts todecode all PDCCHs of the corresponding DCI format for each subframeuntil a PDCCH having an ID thereof is detected and this process isreferred to as blind detection (or blind decoding (BD)).

For example, it is assumed that a specific PDCCH is CRC-masked with aradio network temporary identity (RNTI) ‘A’ and information about datatransmitted using a radio resource ‘B’ (e.g. frequency location) andusing transport format information ‘C’ (e.g. transmission block size,modulation scheme, coding information, etc.) is transmitted in aspecific DL subframe. Then, the UE monitors the PDCCH using RNTIinformation thereof. The UE having the RNTI ‘A’ receives the PDCCH andreceives the PDSCH indicated by ‘B’ and ‘C’ through information of thereceived PDCCH.

Since the UE cannot infinitely perform blind decoding/detection (BS) ina subframe, the number of BD operations that can be performed by the UEin each subframe is defined. In UE-specific search spaces (USSs)including PDCCH candidates that are to carry UE-specific DCI, the numberof PDCCH candidates that the UE should monitor is 16 in total, including6 PDCCH candidates for aggregation level (AL)=1, 6 PDCCH candidates forAL=2, 2 PDCCH candidates for AL 4, and AL=8. In common search spaces(CSSs) including PDCCH candidates that are to carry common DCI, thenumber of PDCCH candidates that the UE should monitor is 6 in total,including 4 PDCCH candidates for AL=4 and 2 PDCCH candidates for AL=8.

FIG. 4 illustrates the structure of a UL subframe used in the LTE/LTE-Abased wireless communication system.

Referring to FIG. 4, a UL subframe may be divided into a data region anda control region in the frequency domain. One or several PUCCHs may beallocated to the control region to deliver UCI. One or several PUSCHsmay be allocated to the data region of the UE subframe to carry userdata.

In the UL subframe, subcarriers distant from a direct current (DC)subcarrier are used as the control region. In other words, subcarrierslocated at both ends of a UL transmission BW are allocated to transmitUCI. A DC subcarrier is a component unused for signal transmission andis mapped to a carrier frequency f₀ in a frequency up-conversionprocess. A PUCCH for one UE is allocated to an RB pair belonging toresources operating on one carrier frequency and RBs belonging to the RBpair occupy different subcarriers in two slots. The PUCCH allocated inthis way is expressed by frequency hopping of the RB pair allocated tothe PUCCH over a slot boundary. If frequency hopping is not applied, theRB pair occupies the same subcarriers.

Recently, machine type communication (MTC) has come to the fore as asignificant communication standard issue. MTC refers to exchange ofinformation between a machine and an eNB without involving persons orwith minimal human intervention. For example, MTC may be used for datacommunication for measurement/sensing/reporting such as meter reading,water level measurement, use of a surveillance camera, inventoryreporting of a vending machine, etc. and may also be used for automaticapplication or firmware update processes for a plurality of UEs. In MTC,the amount of transmission data is small and UL/DL data transmission orreception (hereinafter, transmission/reception) occurs occasionally. Inconsideration of such properties of MTC, it would be better in terms ofefficiency to reduce production cost and battery consumption of UEs forMTC (hereinafter, MTC UEs) according to data transmission rate. Sincethe MTC UE has low mobility, the channel environment thereof remainssubstantially the same. If an MTC UE is used for metering, reading of ameter, surveillance, and the like, the MTC UE is very likely to belocated in a place such as a basement, a warehouse, and mountain regionswhich the coverage of a typical eNB does not reach. In consideration ofthe purposes of the MTC UE, it is better for a signal for the MTC UE tohave wider coverage than the signal for the conventional UE(hereinafter, a legacy UE).

When considering the usage of the MTC UE, there is a high probabilitythat the MTC UE requires a signal of wide coverage compared with thelegacy UE. Therefore, if the eNB transmits a PDCCH, a PDSCH, etc. to theMTC UE using the same scheme as a scheme of transmitting the PDCCH, thePDSCH, etc. to the legacy UE, the MTC UE has difficulty in receiving thePDCCH, the PDSCH, etc. Therefore, the present invention proposes thatthe eNB apply a coverage enhancement scheme such as subframe repetition(repetition of a subframe with a signal) or subframe bundling upontransmission of a signal to the MTC UE having a coverage issue so thatthe MTC UE can effectively receive a signal transmitted by the eNB. Forexample, the PDCCH and PDSCH may be transmitted to the MTC UE having thecoverage issue in a plurality of subframes (e.g. about 100 subframes).

The embodiments of the present invention can be applied to not only the3GPP LTE/LTE-A system but also a new radio access technology (RAT)system. As a number of communication devices have required much highercommunication capacity, the necessity of mobile broadband communication,which is much enhanced compared to the conventional RAT, has increased.In addition, massive MTC capable of providing various services anytimeand anywhere by connecting a number of devices or things to each otherhas been considered as a main issue in the next generation communicationsystem. Moreover, the design of a communication system capable ofsupporting services/UEs sensitive to reliability and latency has alsobeen discussed. That is, the introduction of the next generation RATconsidering the enhanced mobile broadband communication, massive MTC,Ultra-reliable and low latency communication (URLLC), etc. has beendiscussed. For convenience of description, the corresponding technologyis simply referred to as a new RAT in this specification.

In the next system of LTE-A, a method to reduce latency of datatransmission is considered. Packet data latency is one of theperformance metrics that vendors, operators and also end-users (viaspeed test applications) regularly measure. Latency measurements aredone in all phases of a radio access network system lifetime, whenverifying a new software release or system component, when deploying asystem and when the system is in commercial operation.

Better latency than previous generations of 3GPP RATs was oneperformance metric that guided the design of LTE. LTE is also nowrecognized by the end-users to be a system that provides faster accessto internet and lower data latencies than previous generations of mobileradio technologies.

However, with respect to further improvements specifically targeting thedelays in the system little has been done. Packet data latency isimportant not only for the perceived responsiveness of the system; it isalso a parameter that indirectly influences the throughput. HTTP/TCP isthe dominating application and transport layer protocol suite used onthe internet today. According to HTTP Archive(http://httparchive.org/trends.php) the typical size of HTTP-basedtransactions over the internet are in the range from a few 10's ofKbytes up to 1 Mbyte. In this size range, the TCP slow start period is asignificant part of the total transport period of the packet stream.During TCP slow start the performance is latency limited. Hence,improved latency can rather easily be shown to improve the averagethroughput, for this type of TCP-based data transactions. In addition,to achieve really high bit rates (in the range of Gbps), UE L2 buffersneed to be dimensioned correspondingly. The longer the round trip time(RTT) is, the bigger the buffers need to be. The only way to reducebuffering requirements in the UE and eNB side is to reduce latency.

Radio resource efficiency could also be positively impacted by latencyreductions. Lower packet data latency could increase the number oftransmission attempts possible within a certain delay bound; hencehigher block error ration (BLER) targets could be used for the datatransmissions, freeing up radio resources but still keeping the samelevel of robustness for users in poor radio conditions. The increasednumber of possible transmissions within a certain delay bound, couldalso translate into more robust transmissions of real-time data streams(e.g. VoLTE), if keeping the same BLER target. This would improve theVoLTE voice system capacity.

There are more over a number of existing applications that would bepositively impacted by reduced latency in terms of increased perceivedquality of experience: examples are gaming, real-time applications likeVoLTE/OTT VoIP and video telephony/conferencing.

Going into the future, there will be a number of new applications thatwill be more and more delay critical. Examples include remotecontrol/driving of vehicles, augmented reality applications in e.g.smart glasses, or specific machine communications requiring low latencyas well as critical communications.

FIG. 5 illustrates an example of a short TTI and a transmission exampleof a control channel and a data channel in the short TTI.

To reduce a user plane (U-plane) latency to 1 ms, a shortened TTI (sTTI)shorter than 1 ms may be configured. For example, for the normal CP, ansTTI consisting of 2 OFDM symbols, an sTTI consisting of 4 OFDM symbolsand/or an sTTI consisting of 7 OFDM symbols may be configured.

In the time domain, all OFDM symbols constituting a default TTI or theOFDM symbols except the OFDM symbols occupying the PDCCH region of theTTI may be divided into two or more sTTIs on some or all frequencyresources in the frequency band of the default TTI.

In the following description, a default TTI or main TTI used in thesystem is referred to as a TTI or subframe, and the TTI having a shorterlength than the default/main TTI of the system is referred to as ansTTI. For example, in a system in which a TTI of 1 ms is used as thedefault TTI as in the current LTE/LTE-A system, a TTI shorter than 1 msmay be referred to as the sTTI. The method of transmitting/receiving asignal in a TTI and an sTTI according to embodiments described below isapplicable not only to the system according to the current LTE/LTE-Anumerology but also to the default/main TTI and sTTI of the systemaccording to the numerology for the new RAT environment.

In the downlink environment, a PDCCH for transmission/scheduling of datawithin an sTTI (i.e., sPDCCH) and a PDSCH transmitted within an sTTI(i.e., sPDSCH) may be transmitted. For example, referring to FIG. 5, aplurality of the sTTIs may be configured within one subframe, usingdifferent OFDM symbols. For example, the OFDM symbols in the subframemay be divided into one or more sTTIs in the time domain. OFDM symbolsconstituting an sTTI may be configured, excluding the leading OFDMsymbols on which the legacy control channel is transmitted. Transmissionof the sPDCCH and sPDSCH may be performed in a TDM manner within thesTTI, using different OFDM symbol regions. In an sTTI, the sPDCCH andsPDSCH may be transmitted in an FDM manner, using different regions ofPRB(s)/frequency resources.

<OFDM Numerology>

The new RAT system uses an OFDM transmission scheme or a similartransmission scheme. For example, the new RAT system may follow the OFDMparameters defined in the following table. Alternatively, numerologyusing parameters different from those shown in the following table maybe defined. Alternatively, a new RAT system may conform to numerology ofa legacy LTE/LTE-A system but may have a broader system bandwidth (e.g.,100 MHz) than the legacy LTE/LTE-A system. One cell may support aplurality of numerologies. For example, an NR system or an NR cell maysupport a plurality of numerologies in which subcarrier spacings aredifferent. That is, UEs that operate using different numerologies maycoexist within one cell.

TABLE 1 Parameter Value Subcarrier-spacing (Δf) 75 kHz OFDM symbollength 13.33 us Cyclic Prefix(CP) length 1.04 us/0.94 us System BW 100MHz No. of available subcarriers 1200 Subframe length 0.2 ms Number ofOFDM symbol per 14 symbols Subframe

<Analog Beamforming>

In millimeter wave (mmW), the wavelength is shortened, and thus aplurality of antenna elements may be installed in the same area. Forexample, a total of 100 antenna elements may be installed in a 5-by-5 cmpanel in a 30 GHz band with a wavelength of about 1 cm in a2-dimensional array at intervals of 0.5 k (wavelength). Therefore, inmmW, increasing the coverage or the throughput by increasing thebeamforming (BF) gain using multiple antenna elements is taken intoconsideration.

If a transceiver unit (TXRU) is provided for each antenna element toenable adjustment of transmit power and phase, independent beamformingis possible for each frequency resource. However, installing TXRU in allof the about 100 antenna elements is less feasible in terms of cost.Therefore, a method of mapping a plurality of antenna elements to oneTXRU and adjusting the direction of a beam using an analog phase shifteris considered. This analog beamforming method may only make one beamdirection in the whole band, and thus may not perform frequencyselective beamforming (BF), which is disadvantageous.

Hybrid BF with B TXRUs that are fewer than Q antenna elements as anintermediate form of digital BF and analog BF may be considered. In thecase of hybrid BF, the number of directions in which beams may betransmitted at the same time is limited to B or less, which depends onthe method of collection of B TXRUs and Q antenna elements.

<Subframe Structure>

FIG. 6 illustrates the structure of an available subframe in a new radioaccess technology (NR) system.

To minimize data transmission latency, new fifth-generation (5G) RATconsiders a subframe structure in which a control channel and a datachannel are time division multiplexed (TDMed).

In FIG. 6, the hatched area represents the transmission region of a DLcontrol channel (e.g., PDCCH) carrying the DCI, and the black arearepresents the transmission region of a UL control channel (e.g., PUCCH)carrying the UCI. Here, the DCI is control information that the eNBtransmits to the UE. The DCI may include information on cellconfiguration that the UE should know, DL specific information such asDL scheduling, and UL specific information such as UL grant. The UCI iscontrol information that the UE transmits to the eNB. The UCI mayinclude a HARQ ACK/NACK report on the DL data, a CSI report on the DLchannel status, and a scheduling request (SR).

In FIG. 6, the region of symbols from symbol index 1 to symbol index 12may be used for transmission of a physical channel (e.g., a PDSCH)carrying downlink data, or may be used for transmission of a physicalchannel (e.g., PUSCH) carrying uplink data. According to theself-contained subframe structure, DL transmission and UL transmissionmay be sequentially performed in one subframe, and thustransmission/reception of DL data and reception/transmission of ULACK/NACK for the DL data may be performed in one subframe. As a result,the time taken to retransmit data when a data transmission error occursmay be reduced, thereby minimizing the latency of final datatransmission.

In such a self-contained subframe structure, a time gap is needed forthe process of switching from the transmission mode to the receptionmode or from the reception mode to the transmission mode of the eNB andUE. On behalf of the process of switching between the transmission modeand the reception mode, some OFDM symbols at the time of switching fromDL to UL in the self-contained subframe structure are set as a guardperiod (GP).

In a legacy LTE/LTE-A system, a DL control channel is TDMed with a datachannel (refer to FIG. 3) and a PDCCH, which is a control channel, istransmitted throughout an entire system band. However, in new RAT, it isexpected that a bandwidth of one system reaches approximately a minimumof 100 MHz. Therefore, it is difficult to distribute the control channelthroughout the entire band for transmission of the control channel. Fordata transmission/reception of the UE, if the entire band is monitoredto receive the DL control channel, this may cause increase in batteryconsumption of the UE and deterioration of efficiency. Accordingly, thepresent invention proposes a scheme in which the DL control channel canbe locally transmitted or distributively transmitted in a partialfrequency band in a system band, i.e., a channel band.

FIG. 7 illustrates a transmission/reception method of a radio signalusing an analog beam. Particularly, FIG. 7 illustrates atransmission/reception method of a radio signal bytransmission/reception analog beam scanning.

Referring to FIG. 7, if an eNB transmits a synchronization signal in acell or a carrier while switching beams, a UE performs synchronizationwith the cell/carrier using the synchronization signal detected in thecell/carrier and discovers a most suitable (beam) direction for the UE.The UE should be capable of acquiring a cell ID and a beam ID(corresponding to the beam direction) by performing this procedure. TheUE may acquire signals, particularly, RS information, transmitted in thebeam direction, for example, an RS sequence, seed information, andlocation, while acquiring the beam ID. The eNB may allocate a group IDto UEs that have acquired a specific beam ID, i.e., UEs capable ofreceiving a DL channel in a specific beam direction. Cell-commoninformation may be temporally/spatially divided on a beam ID basis andthen transmitted to the UE. The cell-common information may betransmitted to the UE by a beam ID common scheme.

Upon acquiring the beam ID in a cell, the UE may receive cell-specificinformation as beam ID or group ID specific information. The beam ID orgroup ID specific information may be information that UEs of acorresponding group commonly receive.

For convenience of description, a channel on which DL data istransmitted is referred to as a PDSCH and a channel on which UL data istransmitted is referred to as a PUSCH in the present invention. Forconvenience of description, although the present invention is describedfocusing upon a DL environment (transmission of the PDSCH), the presentinvention is applicable even to a UL environment (transmission of thePUSCH).

FIG. 8 illustrates collision caused by transmission of data of twodifferent types on the same time-frequency resource.

When data for which latency is important (e.g., URLLC data) can betransmitted through multiplexing with data for which latency isrelatively less important (e.g., eMBB data) on the same frequencyresource of the same cell, transmission of the data for which latency isimportant may collide with transmission of the data for which latency isless important on the same time-frequency resource. Generally, since thedata for which latency is important is preferentially transmitted, thedata for which latency is important, i.e., PDSCH2, may be transmitted bypuncturing a resource of the data for which latency is less important,i.e., PDSCH1, as illustrated in FIG. 8. In this case, generally, PDSCH1for which latency is less important is transmitted in a TTI longer thana TTI of PDSCH2 for which latency is important. Therefore, generally, apartial region of OFDM symbol(s) of PDSCH1 for which latency is lessimportant is punctured for transmission of PDSCH2 for which latency ismore important. In this case, data, a partial resource region of whichhas been punctured, is subjected to interference on the correspondingresource region and causes remarkable performance deterioration. If a UEthat decodes PDSCH1 is not aware of the presence of PDSCH2 that haspunctured a resource of PDSCH1, since the UE will recognize data locatedon the punctured resource as data of PDSCH1 and decode PDSCH1, errorrate may increase. Accordingly, a method for improving receptionperformance of data punctured for transmission of other data is needed.

The present invention proposes a scheme in which a receiving devicesuccessfully receives data when other data is transmitted in a partialresource (OFDM symbol) region in which data is transmitted in a subframein an NR environment.

Although the present invention is described mainly in consideration ofthe case in which a partial resource (e.g., OFDM symbol) region in whichdata is transmitted is punctured and other data is transmitted in thepunctured resource region, the present invention may be applied even tothe case in which the receiving device cannot correctly receive data ona partial resource on which data is transmitted due to inter-cellinterference.

The present invention may be applied even to the case in which datatransmitted in a legacy TTI or a longer TTI is punctured and transmitteddue to data transmitted in an sTTI in an LTE/LTE-A system as well as anNR environment.

The present invention may also be applied to the case in which datacannot be correctly received due to intra-cell interference and/orinter-cell interference as well as the case in which data is puncturedand transmitted due to transmission of other UL data and/or DL data inan environment using full duplex radio (FDR).

To raise reception performance of data, a partial resource region ofwhich is punctured, the following schemes may be broadly considered inthe receiving device.

Solution A) After a resource region not transmitted due to other dataamong resources of data is punctured, reception and decoding of thecorresponding data is performed.

Solution B) Non-transmitted data (or data failing to be received) isrecovered using an outer erasure code.

Hereinafter, although the present invention will be described under theassumption that a scheme such as Solution A or Solution B is used toraise reception performance of data, a partial resource region of whichis punctured, the present invention may be applied even to the case inwhich other schemes are used.

<A. Method of Determining Location of OFDM Symbols on which Data isPunctured>

When a method such as Solution A as described above is used to raisereception performance of data, a partial resource region of which ispunctured, the receiving device should be aware of a location at whichdata is to be punctured. Generally, since data for which latency isimportant (e.g., PDSCH2 of FIG. 8) is transmitted in the middle oftransmission of data insensitive to a latency issue (e.g., PDSCH1 ofFIG. 8), a UE receiving PDSCH1 is not aware of whether PDSCH2 istransmitted and of a transmission resource on which PDSCH2 istransmitted. Therefore, the UE should receive information about apunctured resource among PDSCH resources received thereby from an eNB.Even when a method such as Solution B is used, the UE may puncturereceived data and determine a data region in which the data is to berecovered through an outer erasure code, by receiving information abouta punctured resource among PDSCH resources received thereby from theeNB. That is, the present invention proposes that whether data ispunctured be indicated through a TTI in which the punctured data ispresent or the next TTI of the TTI in which the punctured data ispresent, in addition to informing the UE of a punctured part when theeNB receives NACK of data transmitted in subframe n and then performsretransmission of the data, the eNB schedules retransmission, or whenthe data is transmitted in subframe n. For example, the indicationmethods may be transmitted through retransmission DCI or an additionalchannel.

To this end, the eNB may indicate an OFDM symbol region in which data ispunctured to the UE as follows.

—Option A1. OFDM Symbol-Wise Indication

FIG. 9 illustrates an example of indicating a punctured OFDM symbolregion according to the present invention.

An eNB may indicate to a UE whether data is punctured on an OFDM symbolbasis or on an OFDM symbol group basis. If it is indicated whether datais punctured on an OFDM symbol group basis to the UE, a region in whichdata is transmitted is classified into a plurality of OFDM symbol groupsand the eNB and the UE may be commonly aware in advance that the datatransmission region is classified into the OFDM symbol groups. TheseOFDM symbol groups may be distinguished by a boundary of a TTI shorterthan a TTI of currently transmitted data. Namely, an OFDM symbol regionbelonging to the same TTI shorter than the TTI of the currentlytransmitted data may belong to the same OFDM symbol group. If there aremultiple TTIs shorter than the TTI of the currently transmitted data,the OFDM symbol groups may be divided based on 1) a boundary of theshortest TTI, or 2) a boundary of a TTI shorter than the TTI in whichthe data is transmitted by one level (i.e., a boundary of the longestTTI among TTIs shorter than the TTI in which the data is transmitted).The following methods may be used to indicate to the UE whether data ispunctured on an OFDM symbol basis or on an OFDM symbol group basis.

Method A1-a) For data transmission, a channel containing informationindicating whether a corresponding OFDM symbol or OFDM symbol group(hereinafter, OFDM symbol (group)) is used may be newly introduced. Inthe present invention, this channel will be referred to as a puncturingindicator channel (PI_CH), for convenience of description. This channelis present on an OFDM symbol basis or on an OFDM symbol group basis, sothat whether an OFDM symbol (group) on which the channel is transmittedor the next OFDM symbol (group) region of the OFDM symbol (group) onwhich the channel is transmitted is used for data transmitted may beindicated to the UE. This indication may be transmitted through thefollowing scheme.

i. 1-bit data is transmitted through the corresponding channel,

ii. a sequence constituting the corresponding channel differs accordingto a value of 1-bit information, or

iii. whether the corresponding channel is transmitted differs accordingto the value of 1-bit information.

Method A1-b) Whether a specific OFDM symbol (group) is used for datatransmission may be indicated to the UE by varying a reference signal(RS) sequence or a scrambling sequence. Herein, the specific OFDM symbol(group) may represent an OFDM symbol (group) on which the RS istransmitted and/or the next OFDM symbol (group) of the OFDM symbol(group) on which the RS is transmitted. For example, when there arescrambling sequence A and scrambling sequence B, if scrambling sequenceA is applied to the RS, this may mean that the OFDM symbol (group) onwhich the RS is transmitted is used for data transmission and, ifscrambling sequence B is applied to the RS, this may mean that the OFDMsymbol (group) on which the RS is transmitted is not used for datatransmission.

Method A1-c) Scrambling may be applied to data on an OFDM symbol (group)basis. That is, one scrambling sequence may be applied to a data parttransmitted on one OFDM symbol (group). In other words, if N OFDMsymbols (groups) are present in a TTI in which data is transmitted, thedata is segmented into N blocks so that scrambling may be applied toeach block and each block may be mapped within one OFDM symbol (group).In this case, whether a specific OFDM symbol (group) is used for datatransmission may be indicated to the UE by varying a scrambling sequenceapplied to data transmitted in each OFDM symbol (group). This specificOFDM symbol (group) may mean an OFDM symbol (group) on which thecorresponding data block is transmitted or the next OFDM symbol (group)of the OFDM symbol (group) on which the corresponding data block istransmitted.

Alternatively, if N OFDM symbols (groups) are present in a TTI in whichdata is transmitted, the data is segmented into N blocks so that acyclic redundant check (CRC) may be attached to each block and eachblock may be mapped within one OFDM symbol (group). In this case,whether a specific OFDM symbol (group) is used for data transmission maybe indicated to the UE by varying a scrambling sequence applied to a CRCof a data block transmitted on each OFDM symbol (group). This specificOFDM symbol (group) may mean an OFDM symbol (group) on which thecorresponding data block is transmitted or the next OFDM symbol (group)of the OFDM symbol (group) on which the corresponding data block istransmitted.

If it is indicated whether the next OFDM symbol (group) region of aspecific OFDM symbol (group) is used for data transmission, anindication of the first OFDM symbol (group) region in a subframe may betransmitted through the last OFDM symbol (group) of a previous subframe.

If Method A1-a) is used, the present invention operates as follows.

Option A1-1) Through the PI_CH, whether an OFDM symbol (group) on whichthe corresponding channel is transmitted is used for data transmissionmay be indicated. In this case, due to transmission of URLLC data usingnumerology different from that of currently transmitted data, a specificOFDM symbol (group) may not be used for transmission of the currentlytransmitted data. In this case, since signal transmission in the OFDMsymbol (group) is performed using different numerologies, it isdifficult to transmit the PI_CH. Accordingly, upon detecting the PI_CH,a receiving device (e.g., UE) may determine that a current OFDM symbol(group) is used for data transmission and, upon not detecting the PI_CH,the receiving device may determine that the current OFDM symbol (group)is not used for data transmission. For example, the UE may performdecoding of corresponding data under the assumption that the data ispresent, i.e., the data has not been punctured, on an OFDM symbol(group) on which the PI_CH is detected. Conversely, the UE may determinethat corresponding data has been punctured on an OFDM symbol group onwhich the PI_CH is not detected and perform decoding by excluding asignal received on the OFDM symbol (group) on which the PI_CH is notdetected from a decoding procedure or decode the signal after recoveringthe signal using an outer erasure code. If an OFDM symbol (group)punctured for data transmission of different numerologies is presentamong OFDM symbols (groups) on which data is transmitted to the UE, theeNB may inform the UE of the location of a punctured resource bytransmitting the PI_CH for an OFDM symbol (group) which is not puncturedto the UE and by not transmitting the PI_CH for an OFDM symbol (group)which is punctured to the UE.

Option A1-2) Through the PI_CH, whether the next OFDM symbol (group) ofan OFDM symbol (group) on which the corresponding channel is transmittedis used for data transmission may be indicated. In this case, thereceiving device may determine that a current OFDM symbol (group) isused for data transmission if the PI_CH is detected. If the PI_CH is notdetected, the receiving device may determine that the current OFDMsymbol (group) is not used for data transmission. However, in this case,the following problems may arise. For example, as illustrated in FIG. 9,when 6 OFDM symbols (OSs) and/or 6 OFDM symbol groups (hereinafter, OSs(groups)) are present, OS (group) #4 may not be used for datatransmission. Hereinafter, in this case, an indication indicating thatdata is not transmitted in OS (group) #4 may be transmitted/receivedthrough OS (group) #3. Meanwhile, if OS (group) #5 is used for datatransmission, this should be indicated through OS (group) #4. However,if signal transmission is performed using different numerologies due toURLLC data transmission on OS (group) #4, since the PI_CH is nottransmitted and the UE cannot detect the PI_CH, the UE may recognizethat OS #5 or OS group #5 is not used for data transmission. To solvethe above problems, the UE may be implemented/configured to determinethat the next OS (group) of an OS (group) indicated not to be used fordata transmission is always used for data transmission.

Option A1-3) In Option A1-1 and Option A1-2, the PI_CH is transmitted onall or almost all OSs (groups) on which data is transmitted. In thiscase, there is disadvantage in that overhead increases due totransmission of the PI_CH. To solve this problem, a transmitting devicemay indicate, through the PI_CH, whether the next OFDM symbol group ofan OFDM symbol (group) (hereinafter, OFDM symbol (group)) on which thecorresponding channel is transmitted is used for data transmission.However, if the PI_CH is not detected, the receiving device maydetermine that a current OFDM symbol (group) is used for datatransmission and, if the PI_CH is detected, the receiving device maydetermine that the current OFDM symbol (group) is not used for datatransmission. In this case, as illustrated in FIG. 9, when 6 OFDMsymbols (groups) are present and OS (group) #4 is not used for datatransmission, the eNB may transmit the PI_CH on OS (group) #3 to causethe UE to determine that OS (group) #4 is not used for data transmissionand may not transmit the PI_CH on OS (group) #4 to cause the UE todetermine that OS (group) #5 is not used for data transmission.

—Option A2. Indication of OFDM Symbol and/or OFDM Symbol Group Used forData Transmission of Previous Subframe in Next Subframe

In subframe #n+k, an OFDM symbol (group) used (or not used) for datatransmission in subframe #n may be indicated. In this case, the subframemay be replaced with an OFDM symbol region or a TTI in which data istransmitted. That is, even if the subframe is replaced with the OFDMsymbol region or the TTI, Option A2 may be applied. An OFDM symbol(group) used (or not used) for data transmission in a specific subframemay be indicated in the next available subframe.

Such an indication may be transmitted through a PDCCH (or DCI) of asubframe in which the indication is given. This indication may becell-specific, UE group-specific, or UE-specific. If the indication iscell-specific or UE group-specific, a PDCCH (or DCI) includinginformation about the indication may be transmitted through a PDCCHcommon search space (CS S) region. The indication may be transmitted bya bitmap scheme with respect to an OFDM symbol (group) constituting asubframe, a TTI or a region in which data is transmitted. Alternatively,the indication may be transmitted by a method of indicating an index (orindexes) of an OFDM symbol (group) used/not used for data transmission.

—Option A3. Indication of OFDM Symbol and/or OFDM Symbol Group Used forData Transmission by Last OFDM Symbol of Subframe

An OFDM symbol (group) used for data transmission may be indicated onthe last OFDM symbol or the last few OFDM symbols of a subframe. In thiscase, the subframe may be replaced with an OFDM symbol region or a TTIin which data is transmitted. That is, even if the subframe is replacedwith the OFDM symbol region or the TTI, Option A3 may be applied.

Method A3-a) A new channel transmitted on the last OFDM symbol or thelast few OFDM symbols of a subframe is introduced and an OFDM symbol(group) used (or not used) for data transmission on this channel may beindicated by the last symbol(s) of the corresponding subframe. Theindication may be transmitted by a bitmap scheme with respect to an OFDMsymbol (group) constituting a subframe, a TTI or a region in which datais transmitted. Alternatively, the indication may be transmitted by amethod of indicating an index (or indexes) of an OFDM symbol (group)used/not used for data transmission.

Method A3-b) An additional code block rather than a code blockconstituting a transport block may be transmitted on the last OFDMsymbol or the last few OFDM symbols of a subframe and an OFDM symbol(group) used (or not used) for data transmission in data constitutingthe additional code block may be indicated by the next availablesubframe. The indication may be transmitted by a bitmap scheme withrespect to an OFDM symbol (group) constituting a subframe, a TTI or aregion in which data is transmitted. Alternatively, the indication maybe transmitted by a method of indicating an index (or indexes) of anOFDM symbol (group) used/not used for data transmission.

<B. Scheme for Successfully Transmitting Data Having Latency IssueDuring UL Transmission>

In a UL environment, when data for which latency is important (e.g.,URLLC data) and data for which latency is relatively less important(e.g., eMBB data) are multiplexed in the same frequency resource of thesame cell and then are transmitted, transmission resources of data ofthe two types may collide. Herein, data for which latency is lessimportant (hereinafter, PUSCH1) may have already been transmitted beforedata for which latency is more important (hereinafter, PUSCH2) istransmitted. In this case, a UE that has transmitted PUSCH1 may continueto transmit PUSCH1 regardless of whether PUSCH2 is scheduled and PUSCH1may act as significant interference with respect to transmission ofPUSCH2 for which latency is relatively important. Therefore, forsuccessful transmission of PUSCH2, methods of reducing an effect onPUSCH1 by PUSCH2 are needed. Hereinafter, such methods are proposed.

—Option B1. Stop of PUSCH Transmission

For successful transmission of PUSCH2, when transmission resources ofPUSCH1 and PUSCH2 overlap, transmission of PUSCH1 may be stopped by thefollowing methods.

Method B1-a) To this end, a new DL channel may be introduced to indicatewhether PUSCH transmission is stopped on the DL channel. In the presentinvention, this channel will be referred to as a PUSCH_Drop channel, forconvenience of description. One or multiple PUSCH_Drop channels may bepresent in a subframe, a TTI or an OFDM symbol region in which data istransmitted and may be located in different time regions (e.g., OFDMsymbols). If stop of PUSCH transmission is indicated on at least onePUSCH_Drop channel while the UE receives the PUSCH_Drop channel(s), theUE may immediately stop PUSCH transmission. In this case, the UE neednot receive a PUSCH_Drop channel which is transmitted after PUSCHtransmission is stopped in a subframe, a TTI, or an OFDM symbol regionin which a corresponding PUSCH has been transmitted. Such an indicationmay be transmitted by the following schemes.

i. 1-bit data is transmitted through the corresponding channel, or

ii. a sequence constituting the corresponding channel differs accordingto a value of 1-bit information.

Method B1-b) Whether PUSCH transmission is stopped may be indicated byvarying a specific DL RS sequence or a scrambling sequence. For example,when there are scrambling sequence A and scrambling sequence B, ifscrambling sequence A is applied to an RS, this means that PUSCHtransmission is not dropped and, if scrambling sequence B is applied tothe RS, this means that PUSCH transmission is dropped. One or plural RSsmay be present in a subframe, a TTI, or an OFDM symbol region in whichdata is transmitted. Scrambling sequences may be independently appliedto RSs located in different time regions (e.g., OFDM symbols). Whilereceiving RSs in different time regions (e.g., OFDM symbols), if ascrambling sequence applied to an RS transmitted in at least one timeregion (e.g., OFDM symbol) indicates that PUSCH transmission is dropped,the UE may immediately stop transmitting a PUSCH.

In this case, an indication/configuration by an eNB, indicating whetherPUSCH transmission is stopped, may be transmitted through a cell/carrierin which data is transmitted. For example, the indication/configurationby the eNB may be transmitted through DCI. Alternatively, uponconsidering a carrier aggregation (CA) and/or dual connectivity (DC)environment, the indication/configuration by the eNB may be transmittedthrough a PCell or a cell/carrier determined by the eNB. In this case,the cell/carrier may be limited to a specific cell/carrier in which DLtransmission is performed during a subframe/time duration in which theUE transmits data. Alternatively, the indication/configuration by theeNB may be configured by any cell/carrier among specific cells/carriersin which DL transmission is performed in a subframe in which the UEreceives data.

—Option B2. Indication of OFDM Symbol and/or OFDM Symbol Group Locationin which PUSCH is Punctured

For successful transmission of PUSCH2, when transmission resources ofPUSCH1 and PUSCH2 overlap, transmission of PUSCH1 may be punctured in anoverlapping OFDM symbol resource. To this end, whether data is puncturedon a corresponding OFDM symbol (group) and/or the next OFDM symbol(group) may be indicated to the UE on an OFDM symbol (group) basis.

Method B2-a) A new DL channel may be introduced to indicate whetherPUSCH transmission is stopped in the DL channel. A plurality of DLchannels may be present with respect to each OFDM symbol (group). Eachchannel may indicate whether PUSCH puncturing is performed on an OFDMsymbol (group) on which the channel is transmitted and/or the next OFDMsymbol (group) of the OFDM symbol (group) on which the channel istransmitted. Such an indication may be transmitted by the followingschemes.

i. 1-bit data is transmitted through the corresponding channel, or

ii. a sequence constituting the corresponding channel differs accordingto a value of 1-bit information.

Method B2-b) Whether a PUSCH is transmitted (whether the PUSCH ispunctured) on a specific OFDM symbol (group) may be indicated to the UEby varying an RS sequence or a scrambling sequence. Herein, the specificOFDM symbol (group) may mean an OFDM symbol (group) on which the RS istransmitted and/or the next OFDM symbol (group) of the OFDM symbol(group) on which the RS is transmitted. For example, when there arescrambling sequence A and scrambling sequence B, if scrambling sequenceA is applied to the RS, this means that the PUSCH is transmitted on theOFDM symbol (group) on which the RS is transmitted and, if scramblingsequence B is applied to the RS, this means that the PUSCH is puncturedon the OFDM symbol (group) on which the RS is transmitted.

In this case, an indication/configuration by the eNB, indicating whetherpuncturing is performed, may be transmitted through a cell/carrier inwhich data is transmitted. Alternatively, upon considering a CA and/orDC environment, the indication/configuration by the eNB may betransmitted through a PCell or a cell/carrier determined by the eNB. Inthis case, the cell/carrier may be limited to a specific cell/carrier inwhich DL transmission is performed during a subframe/time duration inwhich the UE transmits data. Alternatively, the indication/configurationby the eNB may be configured by any cell/carrier among specificcells/carriers in which DL transmission is performed in a subframe inwhich the UE receives data.

—Option B3. Transmission of PUSCH for which Latency is Important at HighPower

For successful transmission of PUSCH2, when another PUSCH has alreadybeen transmitted on a transmission resource of PUSCH2, a possibility oftransmission success of PUSCH2 may be raised by raising transmissionpower of PUSCH2. Herein, the PUSCH may be a PUSCH of a UE that transmitsPUSCH2 or a PUSCH transmitted by a UE different from the UE thattransmits PUSCH2.

Method B3-a) When the eNB schedules a PUSCH transmitted in a short TTI,the eNB may set an absolute value of PUSCH power through DCI forscheduling the PUSCH so that the UE may transmit the PUSCH at high powerregardless of previous PUSCH transmission power. Alternatively, aspecific value of a field for setting the PUSCH power through the DCIfor scheduling the PUSCH may mean a maximum power value or a specificpower value for PUSCH transmission. Alternatively, PUSCH transmissionpower may be set to the maximum power value or the specific power valuethrough an explicit field of the DCI for scheduling the PUSCH.

Method B3-b) URLLC UL data transmitted in an sTTI may always betransmitted at the maximum power value or the specific power value.

Method B3-c) When the UE detects that another signal is beingtransmitted through sensing before transmitting the PUSCH (especially,URLLC UL data transmitted in an sTTI), the URLLC UL data transmitted inthe sTTI may always be transmitted at the maximum power value or thespecific power value.

In Option B3, the specific power value may be defined in the standarddocument or may be a power value configured for the UE through systeminformation or a radio resource control (RRC) signal.

<C. Data Mapping Method for Improving Data Recovery Performance>

When data for which latency is important (hereinafter, PDSCH2) istransmitted by puncturing a resource of data for which latency is lessimportant (hereinafter, PDSCH1), the following methods may be used toreduce an effect of PDSCH2 on PDSCH1. The UE may demap a received signalfrom a resource region under the assumption that the following mappingschemes have been used. The UE may perform decoding based on thedemapped signal.

—Inter-Code Block (CB) Interleaving

Data transmitted on a PDSCH may be segmented into a plurality of codeblocks. In a legacy LTE/LTE-A system, code blocks are sequentiallymapped to resources. For example, code blocks CB0 to CB49 aresequentially mapped to transmission resources according tofrequency-first time-second. In this case, if a partial OFDM symbolregion is punctured by another PDSCH, there is a danger of puncturingmost resources of a specific code block. Accordingly, there is a veryhigh possibility of incorrectly receiving the specific code block. Torandomize interference caused by transmission of other data, atransmitting device may perform interleaving between inter-code blocks.That is, in a process of concatenating a code block, a plurality of codeblocks is not successively concatenated. Instead, one or multiple bitsare selected from a plurality of code blocks randomly or according to aspecific function, thereby performing code block concatenation.Alternatively, after code block concatenation, the concatenated codeblocks may be interleaved randomly or according to a specific function.

—Data Mapping within Sub-PRB

To minimize a resource region punctured by transmission of other data,the transmitting device may transmit data in as wide a PRB region aspossible instead of transmitting data only in a partial frequency regionin one PRB, while transmitting data (or URLLC data) in an sTTI. Forexample, instead of transmitting sTTI data in 25 PRBs, the transmittingdevice may transmit data in 50 PRBs by transmitting data on a half ofsubcarriers (e.g., 6 carriers) per PRB. This may be generalized suchthat the transmitting device may transmit data in N*K PRBs using only1/K subcarriers in one PRB, instead of transmitting data in N PRBs.Thereby, the amount of resources punctured by data (or URLLC data)transmitted in an sTTI may be reduced.

—Time-First Resource Mapping

To prevent a high possibility of incorrectly receiving a specific codeblock because most resources of the code block are punctured, time-firstresource mapping may be performed instead of legacy frequency-firstresource mapping. That is, during data transmission, if an OFDM symbolindex on which data is mapped is t=0, 1, . . . , T and a subcarrierindex on which the data is mapped is f=0, 1, . . . , F, time-firstresource mapping is performed in a direction of first increasing theOFDM symbol index by performing data mapping starting from the lowestsubcarrier index and the lowest OFDM symbol index. If the OFDM symbolindex becomes T, data mapping is performed after setting the OFDM symbolindex t to 0 and increasing the subcarrier index f by 1 so that resourcemapping is performed in a direction of again increasing the OFDM symbolindex. In this way, data mapping may be performed until the OFDM symbolindex t becomes T and the subcarrier index f becomes F. If multiple codeblocks are present, a code block having a low index may be first mappedrelative to a code block having a high index. Thus, if resource mappingis performed, one code block is transmitted throughout the time domain.Accordingly, when a specific OFDM symbol region is punctured orsubjected to interference, a phenomenon in which only the specific codeblock is affected by such puncturing or interference can be prevented.

—Combination of Time-First Mapping and Frequency-First Mapping

To prevent a high possibility of incorrectly receiving a code blockbecause most resources of the code block are punctured, a combination oftime-first resource mapping and frequency-first mapping may be used.

Frequency-first time-second mapping may be performed in each frequencyregion by dividing a frequency region in which data is mapped into aplurality of regions. For example, if a frequency region is divided intoM regions and an index m denoting a frequency region is m=0, 1, . . . ,M, resource mapping may be performed in the following order.

TABLE 2 Set i=0 For n=0, 1, ..., M   For t=0, 1, ..., T    For f =F/M*m, F/M*m+1, ..., F/M*(m+1)−1      Map data symbol s(i) to REcorresponding to frequency index f and OFDM symbol index t      Increasei by 1    end for   end for end for

Alternatively, time-first frequency-second mapping may be performed ineach OFDM symbol region by dividing an OFDM symbol region in which datais mapped into a plurality of regions. For example, if an OFDM symbolregion is divided into N regions and an index n denoting an OFDM symbolregion is n=0, 1, . . . , N, resource mapping may be performed in thefollowing order.

TABLE 3 Set i=0 For n=0, 1, ..., M  For f=0, 1, ..., F    For t = T/N*n,T/N*n+1, ..., T/N*(n+1)−1       Map data symbol (i) to RE correspondingto frequency index f and OFDM symbol index t       Increase i by 1   end for  end for end for

When a transport block is divided into one code block or a small numberof code blocks, the resource mapping scheme may not be needed.Accordingly, in this mapping scheme, the value of M or N may bedetermined based on a modulation and coding scheme (MCS) index, amodulation order, or a transport block size (TBS) (or a TBS index).Alternatively, the value of M or N may be determined according to thenumber of code blocks into which a transport block is divided.Alternatively, the value of M or N applied to data transmission may beconfigured through DCI or an RRC signal.

—Distributed Resource Mapping

FIG. 10 illustrates a resource mapping method according to the presentinvention. A region shown in FIG. 10 represents a resource region inwhich data is mapped and one square denotes one RE. In FIG. 10, a numberwritten on each RE indicates a resource mapping order. In FIG. 10, anempty RE (RE on which a number is not written) indicates that theresource mapping order is omitted.

Meanwhile, to reduce an influence of PDSCH2 on PDSCH1 and to acquireboth time diversity gain and frequency diversity gain, distributedresource mapping may be used. For example, resource mapping may beperformed such that a resource mapping order may be distributed in boththe time domain and the frequency domain in a resource on which data istransmitted by a specific function or rule.

For distributed resource mapping, resource mapping of data may beperformed in a diagonal direction. In time-first resource mapping orfrequency-first resource mapping used in a legacy LTE/LTE-A system, onlyone of a subcarrier index and an OFDM symbol index varies until theindex reaches a boundary of a resource allocation region. In contrast,distributed resource mapping according to the present invention changesboth the subcarrier index and the OFDM symbol index even before theindex reaches a time boundary (i.e., a maximum OFDM symbol index) or afrequency boundary (i.e., a maximum subcarrier index) of a resourceregion allocated to corresponding data. For example, if afrequency-domain resource element (RE) index and a time-domain RE indexare m and n, respectively, then resource mapping of data is performedstarting from an RE in which m=0 and n=0 and each of the indexes m and nof the next RE on which resource mapping is to be performed may beincreased by a (e.g., a=1) relative to the previously used RE indexes.For example, when a is 1, RE indexes which will be used after RE indexesof m=x and n=y may be m=x+1 and n=y+1. To prevent each index fromdeviating from a resource location at which data is transmitted, REindexes which will be used after the RE indexes of m=x and n=y may bem=(x+1) mod M and n=(y+1) mod N. In this case, M may indicate the numberof subcarriers on which a PDSCH is transmitted and N may indicate thenumber of OFDM symbols on which the PDSCH is transmitted. That is, if anRE(m₁, n₁) on which data is first mapped in a mapping order is the firstRE and an RE (m_(i+1), n_(i+1)) is the (i+1)-th RE (i=1, 2, 3, . . . )on which data is mapped, an index pair (m_(i+1), n_(i+1)) of the(i+1)-th RE on which the data is mapped may be given by (m_(i+1),n_(i+1))=((m_(i)+1) mod M, (n_(i)+1) mod N)). An example of suchresource mapping is illustrated in FIGS. 10(a) and 10(b). Particularly,in FIG. 10(a), the number of OFDM symbols on which a PDSCH istransmitted is 14, the number of subcarriers on which the PDSCH istransmitted is 24, and a=1. In FIG. 10(b), the number of OFDM symbols onwhich the PDSCH is transmitted is 2, the number of subcarriers on whichthe PDSCH is transmitted is 24, and a=1. In this case, if resourcemapping has already been performed on an RE on which resource mapping isto be performed, a time index or a frequency index may be increased by b(e.g., b=1). If an RE resource on which data is to be mapped is used byother channels/signals (e.g., RSs), resource mapping may be punctured orrate-matched.

As another example of the distributed resource mapping method,time-first mapping or frequency-first mapping may be performed wherein atime index and/or a frequency index may be increased by an intervalgreater than 1. For example, if resource mapping is performed on an REin which frequency index m=x and time index n=y, RE indexes on whichnext resource mapping is to be performed may be m=x+a and n=y+b whereina and b are integers greater than 1. If an RE index reaches a boundaryof a data transmission resource so that the RE index cannot be increasedany longer, the RE index may be wrapped around and reset to 0. That is,if an RE (m₁, n₁) on which data is first mapped in a mapping order isthe first RE and RE (m_(i+1), n_(i+1)) is the (i+1)-th RE (i=1, 2, 3, .. . ) on which the data is mapped, then an index pair ((m_(i+1),n_(i+1)) of the (i+1)-th RE on which the data is mapped may be given as(m_(i+1), n_(i+1))=((m_(i)+a) mod M, (n_(i)+b) mod N)). FIG. 10(c)illustrates the case in which the number of OFDM symbols on which aPDSCH is transmitted is 2, the number of subcarriers on which the PDSCHis transmitted is 24, a=14, and b=1. In this case, if resource mappinghas already been performed on an RE on which resource mapping is to beperformed, a time index or a frequency index may be increased by c(e.g., c=1). If an RE resource on which data is to be mapped is used byother channels/signals (e.g., RSs), resource mapping may be punctured orrate-matched.

The above-described transmission scheme(s) according to inter-code blockinterleaving, time-first resource mapping, combination mapping oftime-first mapping and frequency-first mapping, and/or distributedresource mapping may be performed as follows.

The above transmission schemes may be applied when one transport blockis divided into a plurality of code blocks. The plural code blocks mayrepresent 1) two or more code blocks, 2) code blocks of a specificnumber or more defined in the standard document, or 3) code blocks of aspecific number or more configured by a system information block (SIB),an RRC signal, etc.

Whether the above transmission schemes are applied to data transmissionmay be indicated through DCI.

Whether the above transmission schemes are applied to data transmissionmay be indicated through an SIB, an RRC signal, etc.

If an importance degree of latency of data is indicated through an SIB,RRC, or DCI and if an indication indicating that latency of data is notimportant is given, it may be assumed that the above transmissionschemes are applied.

To prevent a situation in which a specific frequency region resource ortime region resource is continuously subjected to interference, atransmission scheme may differ during every retransmission. For example,a resource mapping scheme applied during initial transmission and aresource mapping scheme applied during retransmission may differ.Alternatively, an applied resource mapping scheme may differ accordingto a redundancy version (RV) value or a new data indicator (NDI) togglevalue.

Whether the above transmission schemes are applied may differ accordingto an MCS index, a modulation order, or a TBS (or a TBS index). Forexample, if an MCS index, a modulation order or a TBS (or a TBS index)less than a specific value is configured, a legacy resource mappingmethod may be used and, if an MCS index, a modulation order, or a TBsize (or a TBS index) greater than the specific value is configured, theproposed resource mapping methods may be applied.

<D. Data Reception Method Through Blind Decoding>

For the eNB to transmit data to a UE for which latency is important(e.g., URLLC UE), the eNB may puncture data transmitted to a UE forwhich latency is relatively less important and transmit the data of theUE for which latency is important at a corresponding resource location.In this case, the UE for which latency is relatively less important mayuse the following method to successfully receive data although a part ofthe data transmitted to the UE is punctured. In the present invention, aUE for which latency is important is referred to as a URLLC UE and a UEfor which latency is relatively less important is referred to as an eMBBUE, for convenience of description.

First, the eNB may indicate one or multiple candidate resources on whichdata can be punctured to the eMBB UE. This information may be configuredthrough RRC or DCI. When data is transmitted to the eMBB UE through RRCor DCI, the eMBB UE may determine that data is transmitted on a resourceconfigured for the eMBB UE without any puncturing or that data istransmitted through puncturing, using the puncturing candidate resourcesindicated by the eNB or one (or plural) candidate resources among thepuncturing candidate resources. When data is transmitted to the eMBB UE,the eMBB UE is not aware of whether puncturing has actually beenperformed and of a puncturing resource location. Therefore, the eMBB UEmay attempt to receive data through blind decoding with respect to thecase in which puncturing is not used and the case in which data has beenpunctured using the puncturing candidate resources indicated by the eNBor one (or plural) candidate resources among the puncturing candidateresources.

For example, if puncturing resource candidate locations 1 and 2 arepresent in an eMBB transmission resource, the eNB may configureinformation about the resource locations for the eMBB UE. For example,the puncturing resource candidate location 1 may be OFDM symbol #m andthe puncturing resource candidate location 2 may be OFDM symbol #n. Inthis case, during data reception, the eMBB UE may perform blinddetection with respect to the case in which data is transmitted withoutpuncturing, the case in which data is transmitted with puncturing at thepuncturing resource candidate location 1, the case in which data istransmitted with puncturing at the puncturing resource candidatelocation 2, and/or the case in which data is transmitted with puncturingat both the puncturing resource candidate locations 1 and 2.

FIG. 11 is a block diagram illustrating elements of a transmittingdevice 10 and a receiving device 20 for implementing the presentinvention.

The transmitting device 10 and the receiving device 20 respectivelyinclude Radio Frequency (RF) units 13 and 23 capable of transmitting andreceiving radio signals carrying information, data, signals, and/ormessages, memories 12 and 22 for storing information related tocommunication in a wireless communication system, and processors 11 and21 operationally connected to elements such as the RF units 13 and 23and the memories 12 and 22 to control the elements and configured tocontrol the memories 12 and 22 and/or the RF units 13 and 23 so that acorresponding device may perform at least one of the above-describedembodiments of the present invention.

The memories 12 and 22 may store programs for processing and controllingthe processors 11 and 21 and may temporarily store input/outputinformation. The memories 12 and 22 may be used as buffers.

The processors 11 and 21 generally control the overall operation ofvarious modules in the transmitting device and the receiving device.Especially, the processors 11 and 21 may perform various controlfunctions to implement the present invention. The processors 11 and 21may be referred to as controllers, microcontrollers, microprocessors, ormicrocomputers. The processors 11 and 21 may be implemented by hardware,firmware, software, or a combination thereof. In a hardwareconfiguration, application specific integrated circuits (ASICs), digitalsignal processors (DSPs), digital signal processing devices (DSPDs),programmable logic devices (PLDs), or field programmable gate arrays(FPGAs) may be included in the processors 11 and 21. Meanwhile, if thepresent invention is implemented using firmware or software, thefirmware or software may be configured to include modules, procedures,functions, etc. performing the functions or operations of the presentinvention. Firmware or software configured to perform the presentinvention may be included in the processors 11 and 21 or stored in thememories 12 and 22 so as to be driven by the processors 11 and 21.

The processor 11 of the transmitting device 10 performs predeterminedcoding and modulation for a signal and/or data scheduled to betransmitted to the outside by the processor 11 or a scheduler connectedwith the processor 11, and then transfers the coded and modulated datato the RF unit 13. For example, the processor 11 converts a data streamto be transmitted into K layers through demultiplexing, channel coding,scrambling, and modulation. The coded data stream is also referred to asa codeword and is equivalent to a transport block which is a data blockprovided by a MAC layer. One transport block (TB) is coded into onecodeword and each codeword is transmitted to the receiving device in theform of one or more layers. For frequency up-conversion, the RF unit 13may include an oscillator. The RF unit 13 may include N_(t) (where N_(t)is a positive integer) transmit antennas.

A signal processing process of the receiving device 20 is the reverse ofthe signal processing process of the transmitting device 10. Undercontrol of the processor 21, the RF unit 23 of the receiving device 20receives radio signals transmitted by the transmitting device 10. The RFunit 23 may include N_(r) (where N_(r) is a positive integer) receiveantennas and frequency down-converts each signal received throughreceive antennas into a baseband signal. The processor 21 decodes anddemodulates the radio signals received through the receive antennas andrestores data that the transmitting device 10 intended to transmit.

The RF units 13 and 23 include one or more antennas. An antenna performsa function for transmitting signals processed by the RF units 13 and 23to the exterior or receiving radio signals from the exterior to transferthe radio signals to the RF units 13 and 23. The antenna may also becalled an antenna port. Each antenna may correspond to one physicalantenna or may be configured by a combination of more than one physicalantenna element. The signal transmitted from each antenna cannot befurther deconstructed by the receiving device 20. An RS transmittedthrough a corresponding antenna defines an antenna from the view pointof the receiving device 20 and enables the receiving device 20 to derivechannel estimation for the antenna, irrespective of whether the channelrepresents a single radio channel from one physical antenna or acomposite channel from a plurality of physical antenna elementsincluding the antenna. That is, an antenna is defined such that achannel carrying a symbol of the antenna can be obtained from a channelcarrying another symbol of the same antenna. An RF unit supporting aMIMO function of transmitting and receiving data using a plurality ofantennas may be connected to two or more antennas.

In the embodiments of the present invention, a UE operates as thetransmitting device 10 in UL and as the receiving device 20 in DL. Inthe embodiments of the present invention, an eNB operates as thereceiving device 20 in UL and as the transmitting device 10 in DL.Hereinafter, a processor, an RF unit, and a memory included in the UEwill be referred to as a UE processor, a UE RF unit, and a UE memory,respectively, and a processor, an RF unit, and a memory included in theeNB will be referred to as an eNB processor, an eNB RF unit, and an eNBmemory, respectively.

The eNB processor may control the eNB RF unit to transmit DL dataaccording to the proposal of the present invention described in SectionA. The eNB processor may control the eNB RF unit to transmit puncturinginformation indicating a punctured part to the UE. The UE processor maycontrol the UE RF unit to receive the DL data according to the proposalof the present invention described in Section A. The UE processor mayrecover or decode the DL data, under the assumption that a signal is notpresent in a part in which the DL data is punctured, based on puncturinginformation according to the proposal of the present invention describedin Section A.

The eNB processor may control the eNB RF unit to receive UL dataaccording to the proposal of the present invention described in OptionA3 of Section A. The UE processor may control the UE RF unit to transmitthe UL data according to the proposal of the present invention describedin Option A3 of Section A.

The UE processor may control the UE RF unit to transmit a PUSCH or stoptransmitting the PUSCH according to the proposal of the presentinvention described in Section B. The eNB processor may control the eNBRF unit to receive the PUSCH or stop receiving the PUSCH according tothe proposal of the present invention described in Section B.

The eNB processor may map DL data to a time-frequency resource region towhich the DL data is allocated according to the proposal of the presentinvention described in Section C. The UE processor may recover or decodethe DL data under the assumption that the DL data is mapped in thetime-frequency resource region to which the DL data is allocatedaccording to the proposal of the present invention described in SectionC. That is, the UE processor may demap a signal received in thetime-frequency resource region according to the proposal of the presentinvention described in Section C and decode the demapped signalaccording to the proposal of the present invention described in SectionC.

The UE processor may blind-detect a punctured resource according to theproposal of the present invention described in Section D of the presentinvention.

As described above, the detailed description of the preferredembodiments of the present invention has been given to enable thoseskilled in the art to implement and practice the invention. Although theinvention has been described with reference to exemplary embodiments,those skilled in the art will appreciate that various modifications andvariations can be made in the present invention without departing fromthe spirit or scope of the invention described in the appended claims.Accordingly, the invention should not be limited to the specificembodiments described herein, but should be accorded the broadest scopeconsistent with the principles and novel features disclosed herein.

INDUSTRIAL APPLICABILITY

The embodiments of the present invention are applicable to an eNB, a UE,or other devices in a wireless communication system.

1. A method of receiving downlink data by a user equipment, the methodcomprising: receiving the downlink data in a first time interval;receiving downlink control information in a second time interval; anddecoding the downlink data based on the downlink control information,wherein the first time interval includes multiple orthogonal frequencydivision multiplexing (OFDM) symbols in a time domain, and wherein thedownlink control information includes information on one or more OFDMsymbols, in which the downlink data is not present, among the multipleOFDM symbols belonging to the first time interval preceding the secondtime interval in the time domain.
 2. The method according to claim 1,wherein the multiple OFDM symbols in the first time interval are dividedinto a plurality of OFDM symbol groups in the time domain, and whereinthe information on the one or more OFDM symbols in which the downlink isnot present includes a bitmap having a plurality of bits, wherein theplurality of bits are corresponding to the plurality of OFDM symbolsgroups, respectively, and wherein each of the plurality of bitsindicates whether the downlink data is present in a corresponding OFDMsymbol group.
 3. The method according to claim 1, wherein the downlinkcontrol information is received through a physical downlink controlchannel on a common search space in the second time interval. 4.(canceled)
 5. The method according to claim 1, wherein the one or moreOFDM symbols in which the downlink data is not present include atime-frequency resource punctured by latency-critical data. 6.(canceled)
 7. (canceled)
 8. A user equipment for receiving downlinkdata, the user equipment comprising: a transceiver, and a processorconfigured to control the transceiver, the processor configured to:control the transceiver to receive the downlink data in a first timeinterval; control the transceiver to receive downlink controlinformation in a second time interval; and decode the downlink databased on the downlink control information, wherein the first timeinterval includes multiple orthogonal frequency division multiplexing(OFDM) symbols in a time domain, and wherein the downlink controlinformation includes information on one or more OFDM symbols, in whichthe downlink data is not present, among the multiple OFDM symbolsbelonging to the first time interval preceding the second time intervalin the time domain.
 9. (canceled)
 10. A base station for transmittingdownlink data, the base station comprising: a transceiver, and aprocessor configured to control the transceiver, the processorconfigured to: control the transceiver to transmit first downlink datain a first time interval to a user equipment; control the transceiver totransmit second downlink data by puncturing a part of a time-frequencyresource allocated to the first downlink data; and control thetransceiver to transmit downlink control information in a second timeinterval to the user equipment wherein the first time interval includesmultiple orthogonal frequency division multiplexing (OFDM) symbols in atime domain, and wherein the downlink control information includesinformation on one or more OFDM symbols, in which the first downlinkdata is not present, among the multiple OFDM symbols belonging to thefirst time interval preceding the second time interval in the timedomain.
 11. The method according to claim 1, wherein the downlink datais received on a time-frequency resource in the first time intervalbased on a combination resource mapping scheme or a distributed resourcemapping scheme, wherein the combination resource mapping scheme maps thedownlink data by a time-first frequency-second mapping scheme in each ofX time regions included in the time-frequency resource, where X is aninteger greater than 1, and wherein the distributed resource mappingscheme maps the downlink data in a diagonal direction in thetime-frequency resource. 12-19. (canceled)
 20. The user equipmentaccording to claim 8, wherein the multiple OFDM symbols in the firsttime interval are divided into a plurality of OFDM symbol groups in thetime domain, and wherein the information on the one or more OFDM symbolsin which the downlink data is not present includes a bitmap having aplurality of bits, wherein the plurality of bits are corresponding tothe plurality of OFDM symbols groups, respectively, and wherein each ofthe plurality of bits indicates whether the downlink data is present ina corresponding OFDM symbol group.
 21. The user equipment according toclaim 8, wherein the downlink control information is received through aphysical downlink control channel on a common search space in the secondtime interval.
 22. The user equipment according to claim 8, wherein theone or more OFDM symbols in which the downlink data is not presentinclude a time-frequency resource punctured by latency-critical data.23. The base station according to claim 10, wherein the multiple OFDMsymbols in the first time interval are divided into a plurality of OFDMsymbol groups in the time domain, and wherein the information on the oneor more OFDM symbols in which the first downlink data is not presentincludes a bitmap having a plurality of bits, wherein the plurality ofbits are corresponding to the plurality of OFDM symbols groups,respectively, and wherein each of the plurality of bits indicateswhether the first downlink data is present in a corresponding OFDMsymbol group.
 24. The base station according to claim 10, wherein thedownlink control information is transmitted through a physical downlinkcontrol channel on a common search space in the second time interval.25. The base station according to claim 10, wherein the one or more OFDMsymbols in which the first downlink data is not present include the partof the time-frequency resource, and wherein the second downlink data islatency-critical data.
 26. The base station according to claim 10,wherein the processor is configured to map the first downlink data tothe time-frequency resource allocated to the user equipment, wherein thefirst downlink data is mapped to the time-frequency resource based on acombination resource mapping scheme or a distributed resource mappingscheme, wherein the combination resource mapping scheme maps the firstdownlink data by a time-first frequency-second mapping scheme in each ofX time regions included in the time-frequency resource, where X is aninteger greater than 1, and wherein the distributed resource mappingscheme maps the first downlink data in a diagonal direction in thetime-frequency resource.